Blood Tests: Definition, Importance, Uses, and Types

The blood test is a diagnostic procedure conducted on the blood for disease diagnosis, health monitoring and to assess the efficacy of treatment. The blood is collected from the peripheral veins through a finger prick or a hypodermic needle and is subjected to various types of blood tests. Blood testing is important for doctors to find any possible issues, the test give people a better overview of their health and there are many uses for blood tests.

Blood testing is a useful tool for diagnosing diseases and regular health monitoring. The blood tests like liver function tests and kidney function tests help physicians to assess the health status of different organs. Some blood test results help physicians see how the treatment regime is working. Different blood work is available, which, alone or in combination with other tests, aid the healthcare providers in their job.

What are Blood Tests?

Blood testing refers to the analysis of things found in your blood. The red fluid (blood) flowing inside the vessels is involved in almost all body functions. Various chemicals produced in the body, the causative agents of bacterial, viral, parasitic, and fungal infections and their antigens, etc., enter the blood. The dynamics of blood, i.e., the number proportion of different types of blood cells and the shapes of these cells, also change whenever there is something wrong inside the body. The blood tests detect all these changes, and the blood test results allow the physicians to make decisions related to diagnosis, treatment, and prognosis.

What is Blood Work?

Blood work is the scientific examination of blood samples for disease diagnosis and health monitoring. Blood is just like a city’s transportation system. Everything moving in and out of the city passes through this system. Various types of blood cells are just like vehicles moving on the roads. Blood forms nearly 10% of the adult body weight, and blood cells are the most abundant cells in the body. 

Blood has many functions in the body. It transports oxygen from the lungs to all body parts and removes the waste gases (carbon dioxide) from the body. Haemoglobin, a red-coloured pigment on the red blood cells, is specialised for this purpose. The blood absorbs nutrients from the digestive system and transports them to all body cells. It defends the body against germs. The white cells in the body are the soldiers who fight intruders and kill them. In response to the complicated infections, these white cells differentiate into various specialised cells for a better fight. Some blood cells (B lymphocytes) produce antibodies important to the body’s defence system, while others (e.g., lymphocytes, macrophages, neutrophils, etc.) kill the germs by engulfing them. It is a running reservoir containing vitamins, glucose, fat molecules (e.g., cholesterol), water (nearly 50%2 of blood is water), salts, hormones, various enzymes, proteins (albumin, globulin, fibrinogen), various nutrients, and the nitrogenous waste compounds and is involved in the homeostasis of these substances. 

It helps in the healing process. For example, some blood cells (the platelets) form a clot at the site of the wound and stop the bleeding.  It helps remove nitrogenous waste products from the body as it brings the waste products into the liver and kidney, where they are removed.  It helps to maintain body temperature. The evaporation of water from the blood vessels and their contraction and expansion help in thermoregulation. 

Why are Blood Tests important? 

Blood test are important because various types of blood tests are useful for different purposes. Broadly, they are used for disease diagnosis, to monitor the functioning of various body organs, and to monitor the progression of a treatment plan. Blood tests are performed whenever needed and are included in the annual health monitoring program. 

Blood culture tests detect the presence of germs in the blood. The antigen tests detect the presence of bacteria/viral antigens and the antibody tests detect the presence of various antibodies produced in response to the antigens. These tests also show the effectiveness of the immune response. The level tests monitor the levels of different blood molecules, e.g., cholesterol, glucose, proteins, etc., in the blood.  Blood cell count tests (e.g., CBC) determine the counts of various cells in the blood. The biomarker tests detect the presence of various biomarkers in the blood, e.g., the biomarkers related to heart health. The lipid profile shows the levels of triglycerides, total lipids, and cholesterol in the blood. The coagulation and clotting tests show the functioning of platelets, clotting factors, and some inherited coagulation disorders. Nutrient deficiency tests detect the deficiencies of essential nutrients, e.g., minerals and vitamins. The enzyme tests detect the levels of various enzymes in the body. 

What Are the Uses of Blood Tests?

Blood tests are useful for a variety of purposes. The blood analysis provides the easiest way to access the overall health status. The blood work helps to monitor the functions of different body organs, diagnose nutritional deficiencies, help access the health of the immune system and assess the effectiveness of a treatment plan, etc. The healthcare provider can ask for blood tests to assess the general health status. 

What are the Different Types of Blood Tests?

Listed below are the different types of the blood test. 

• Liquid Panel: This test detects the levels of cholesterol and triglycerides in the blood.
• Comprehensive Metabolic Panel: These tests detect markers associated with metabolism e.g., blood proteins, minerals, blood glucose etc. 
• Basic Metabolic Panel: It is a shorter version of the comprehensive metabolic panel and does not include the liver function tests. 
• Complete Blood Count: It monitors the counts of different blood cells e.g., erythrocytes, platelets and leukocytes.
• Thyroid Panel: It detects the levels of thyroid hormones T3, T4 nad TSH and helps diagnose hypothyroidism and hyperthyroidism. 
• C-Reactive Protein Test: It detects the presence of c-reactive protein (CRP) produced in response to any inflammation infection in the body. 
• Cardiac Biomarkers: These tests detect various biomarkers released in response to an adverse cardiovascular health event.
• Coagulation Panel: These tests detect various factors involved in clotting and help diagnose clotting diseases. 
• Blood Clotting Tests: These tests detect various blood proteins involved in blood clotting. 
• Sexually Transmitted Infection Tests: These tests diagnose sexually transmitted infections e.g., syphilis, gonorrhea and trichomoniasis. 
• Dhea-Sulfate Serum Test: This blood test detects the level of DHEA-sulfate in the blood and monitors the adrenal gland's health. 
• Blood Enzyme Tests: These tests detect the level of different enzymes in the blood. 

1. Lipid Panel

The lipid panel of lipid profile includes various tests which detect the levels of lipids in the blood. These tests measure the levels of cholesterols and triglycerides in the blood, which are important risk factors for cardiovascular diseases. Doctors use these tests for adults and children to determine the risk of cardiovascular diseases and to advise patients about healthcare and diets. Various variants of this test are available, e.g., the fasting and non-fasting lipid profile, lipid test, cholesterol panel, and coronary risk panel. 

Various types of tests in the lipid panel are used to measure various types of fats. For example, 

Triglyceride test: Triglycerides are the fat molecules found in the blood, and their excessive presence would mean an increased risk of cardiovascular health issues. The triglyceride level in the blood should be less than 150 mg/ dL.

Total cholesterol: This test measures the sum of all cholesterol in the blood. The total cholesterol in the blood should be less than 200 mg/ dL. 

LDL cholesterol: LDL cholesterol means low-density lipoprotein and reflects the bad cholesterol in the blood. Its accumulation can be dangerous. The LDL cholesterol in the blood should be less than 100 mg/ dL. 

HDL cholesterol: HDL cholesterol means high-density lipoprotein. It is good cholesterol because the body requires it for various functions. The HDL cholesterol in the blood should be less than 40 mg/ dL. 

VLDL cholesterol means very low-density lipoprotein, and its levels are lower than the other cholesterols. The normal level should be less than 30 mg/ dL. Its higher levels during fasting mean hypercholesterolemia. 

Besides monitoring the risk of cardiovascular diseases, these tests also tell the doctors about the liver's health. The interpretation of results in the doctor's job depends upon various factors, e.g., age, health status, gender, pregnancy and breastfeeding, presence of offer diseases, etc. 

The frequency of testing is variable. All adults should check cholesterol regularly every 4-6 years.  The interval could be lowered to 1-2 years for men 45-65 years of age and women 55-65 years of age. Some conditions, e.g., exposure to cardiac risk factors, require annual or even more robust screening.

2. Comprehensive Metabolic Panel

The Comprehensive Metabolic Panel is a comprehensive test panel covering 14 parameters related to metabolism, e.g., the levels of important enzymes, essential nutrients, and the enzymes linked to kidney and liver functions. All these 14 parameters provide the physician with information about overall physical well-being. The CMP is recommended for the following reasons;

• Diagnosing different health conditions, e.g., diabetes, nutritional deficiencies, liver and kidney issues, etc. 
• Regular screening of various health issues at early stages. 

Let's see the different parameters in this profile and what should be the normal values of these parameters.

Alanine aminotransferase (ALT): ALT is an enzyme produced in the liver. Its levels are increased in response to liver damage. Different laboratories use various reference values, but the commonly quoted range is 5-40 U/ L, with minor variations in both genders. Some sources consider up to 55 IU/ L to be normal.

Albumin is a protein produced by the liver and found in the blood. It helps in the transportation of molecules and also maintains the osmotic balance of the blood. Its normal range is 3.5-4 g /dL (35-40 g/L). 

Alkaline phosphatase (ALP): This enzyme is found throughout the body but is concentrated in the bones and liver. Its normal range is 36-150 U/ L. 

Bilirubin: It is a yellowing-coloured waste product of red blood cell breakdown. Its high levels mean an excessive breakdown of red blood cells.  The normal range of total bilirubin and conjugated bilirubin (direct)  in the blood is 0.3-1.2 mg/dL and 0-0.3 mg/ dL.

Aspartate aminotransferase (AST): This hormone is found in the liver and many other body tissues. Its normal level should be less than 35 U/ L. 

Blood urea nitrogen (BUN): It's a waste product that is excreted by the kidneys, and its levels are used to assess kidney health. Its normal range is 8-20 mg/ dL. 

Creatinine: It is a water product of the metabolism of muscles. Its high levels mean the excessive breakdown of muscles, and lower levels mean low muscle mass. Its normal range is 0.7-1.2 mg/dL for men and 0.5-1.0 mg/dL for women. 

Total proteins: This test measures the total proteins (albumin+ globulins) and assesses the health of blood and immune functions. The normal range of TP is 6-8.3 g/dL or 60-83 g/ L. 

Glucose: Blood glucose is a source of instant energy for body organs. Its high or low levels indicate problems with glucose metabolism, e.g., diabetes. The normal range depends upon several variables, and for healthy young people, it should be less than 100 mg/ dL. Between 100-125 indicate prediabetic condition and values above it mean diabetes. 

Bicarbonate: This electrolyte is used by the body to remove carbon dioxide from the body. Its deficiency or excess will cause problems with the blood pH. The normal range is 23-28 mEq/ L. 

Calcium: This mineral comes from food and is stored in the bones. It is necessary for the health and functioning of muscles, bones, and nervous and cardiovascular systems. The normal range in the serum should be 9-10.5 mg/ dL. 

Chloride:  This mineral is an important part of mineral homeostasis and has various functions. Its serum levels should be 98-106 mEq/ L. 

Sodium: This mineral is necessary for acid-base and fluid balance in the body and the proper nerve and muscle function. Its dietary intake and renal excretion should be balanced to achieve the normal range between 136-145 mEq/ L. 

Potassium: This electrolyte comes from the diet and is present in all body tissues and the blood. Its level should be 3.5-5.0 mEq/ L. 

Most people use CMP as a part of a yearly health monitoring program, particularly after 40-45 years of age. It allows the doctor to take a record of any chronic health conditions and take advice on healthcare and diets.

3. Basic Metabolic Panel (BMP)

It is a smaller version of the complete metabolic panel and detects 8 parameters (instead of 14). It provides physicians with important information about the metabolism and homeostasis in the body. The following tests are included in the BMP;

• Blood urea nitrogen (BUN)
• Creatinine
• Sodium
• Chloride 
• Potassium
• Carbon dioxide (CO2)
• Calcium
• Blood glucose

These tests' indications and normal ranges are similar to those mentioned in the CMP. These tests provide important information about the metabolism, acid-base balance, glucose metabolism, electrolyte and fluid balance, and the functioning of the kidneys. It is recommended when the physician is more or less satisfied with the health of the liver and the blood proteins. It is also recommended to be included in the yearly health monitoring program after 40-45 years of age. For younger people, the physician can increase the interval.

4. Complete Blood Count (CBC)

The CBC is a blood test that measures various blood fractions and informs the doctor about any abnormality in the blood or blood-forming organs. This test is a part of routine health monitoring. Doctors often recommend it in case of any infections and for diagnosing conditions like blood cancer, immune system diseases, anaemia, etc. The CBC is often the first test to be asked by the physician in case of any health issue. The various parameters included in this test and their normal values are;

Red blood cell count: These cells carry oxygen from the lungs to various body parts and are the most abundant cell type in the blood and the whole body. The reference values are;

• For men: 4.5- 5.9 million per microliter (4.5-5.9x1012 cells/ L)
• For women: 4-5.2 million per microliter (4-5.2x1012 cells/ L)

Total leukocyte count (TLC): The leukocytes, also known as the white blood cells, defend the body against germs. They are of 5 different types. However, the TLC provides a sum of all these categories. The reference values are; 

• For men and women: 4500-11000 cells per microliter (4.5-11x109 cells/ L)

The TLC is increased in case of infections and decreased in case of immunosuppression. 

Differential leukocyte count (DLC): This test measures the number and proportions of different types of leukocytes in the blood. It's important as different types of leukocytes increase in number in different situations. Their values are given as percentages (%) of all leukocytes. 

The normal values are;

Lymphocytes

• Men and women: 1000-4800 cells per microliter (1-4.8x109 cells/ L) or 22-44% of all leukocytes

Monocytes

• Men and women: 200-1200 cells per microliter (0.2.1.2x109 cells/ L) or 4-11% of all leukocytes

Neutrophils

• Men and women: 1800-7700 cells  per microliter (1.8-7.7x109 cells/ L) or 40-70% of all leukocytes

Eosinophils

• Men and women: 0.900 cells per microliter (0.0.9x109 cells/ L) or 0-8% of all leukocytes

Basophils

• Men and women: 0-300 cells per microliter (0-0.3x109 cells/ L) or 0-3% of all leukocytes

Platelet count: This test detects the number of platelets in the blood, which play an important role in the body by clotting the blood. The reference values are;

• Men and women: 140,000-450,000 cells per microliter (140-450x109 cells/ L) 

Hematocrit:  It is a fractional measure and tells how many blood fractions are formed by the red blood cells. The reference values are different for both genders and are

• Men: 41-55%
• Women: 36-47%

Haemoglobin: Haemoglobin is a red pigment that carries oxygen. The red blood cells are the balls loaded with haemoglobin. Its reference values also vary between genders.

• For men:  14-17 g/ dL (140-170 g/ L)
• Women: 12-16 g/ dL (120-160 g/ L)

Mean corpuscular volume (MCV):  It measures the average size of the red blood cells. The reference values are;

• For all genders: 80-100 femtoliters/ cell

Mean corpuscular haemoglobin (MCH): This cell measures the amount of haemoglobin present in each cell. The reference range is:

• For all genders: 28-32 picograms/ cell

Mean corpuscular haemoglobin concentration (MCHC): This test measures the average haemoglobin concentration in each red blood cell. The reference range is

• For all genders: 32-36 grams/ dL of RBCs

The CBC is included in the yearly health monitoring program. Still, the doctor can recommend it whenever needed, e.g., in case of suspected infections, diseases of the blood-forming organs, or in case of blood transfusion or donation.

5.Thyroid Panel

A thyroid panel blood test is used to assess the thyroid gland's health status and monitor the treatment of thyroid gland diseases, e.g., thyroid cancer, thyroid nodule, hypothyroidism, hyperthyroidism, goitre, Grave's disease, thyroiditis, etc. The panel includes various tests that inform the doctor about the condition of the thyroid gland. The tests included in this panel and their reference values are;

TSH test: TSH means the thyroid stimulating hormone. This hormone is produced by the pituitary gland and regulates the production of thyroid hormones. Its levels are elevated in hypothyroidism and lower in hyperthyroidism. Its level is measured in the serum, and the normal range is;

• For all genders: 0.5-5.0 mIU/ L. 

Triiodothyronine (T3): The levels of this hormone are determined to detect hypothyroidism or hyperthyroidism.  Its level is measured in the serum, and the normal range is;

• For all genders: 70-195 ng/ dL

Free triiodothyronine (FT3):  This test measures the amount of free T3 in the blood which is not bound to the blood proteins. Its level is also measured in the serum, and the normal range is;

• For all genders: 2.0-4.4 picograms/ mL

Thyroxine (T4): The levels of this hormone are used to diagnose hypothyroidism and hyperthyroidism and to see the efficacy of thyroid treatment.  Its level is also measured in the serum, and the normal range is;

• For all genders:  5-12 mcg/ dL

Free thyroxine (FT4): This test measures the amount of T4, which is not bound to blood proteins and is free.  Its level is also measured in the serum, and the normal range is;

• For all genders: 0.93-1.70 ng/ dL

Thyroglobulin: Thyroglobulin is a thyroid protein produced by the follicular cells and used by the thyroid gland to produce hormones. The abnormal levels show thyroiditis or thyroid cancer. The normal values depend upon gender and are;

• Men: 1.40-29.2 ng/ mL
• Women: 1.50-38.5 ng/ mL

Calcitonin: Calcitonin is a hormone produced by the thyroid gland that regulates calcium metabolism. Its level is used to diagnose thyroid cancer and C- cell hyperplasia, a rare thyroid disease. Its normal range is different for both men and women and is;

• Men: equal to or less than 8.4 pg/ mL.
• Women: equal to or less than 5 pg/ mL.

Thyroid antibodies: These tests detect various antibodies produced in autoimmune conditions of the thyroid gland, e.g., thyroid-blocking immunoglobulins (TBIs), thyroglobulin antibodies, etc. The doctor interprets the test results. 

Like other tests, thyroid panels should be included in the annual health monitoring program. However, some situations, e.g., thyroid surgery, medications, infections, etc., can require more frequent testing.

6. C-Reactive Protein (CRP) Test

This test measures the level of C-reactive protein in the blood sample. It's a liver protein, and its level increases in case of inflammation, infection, or injury. The CRP test can monitor chronic and acute inflammations (e.g., Crohn's disease, ulcerative colitis, inflammatory bowel disease, etc.), infections, and autoimmune diseases, e.g., vasculitis, rheumatoid arthritis, lupus, etc. This test can also be used to see the response to the treatment. Various levels of CRP and their clinical interpretations are;

Normal levels

This protein is produced in response to inflammation. So, there is nothing like a "normal value." However, for simplification, values less than 0.3 mg/ dL are considered normal in healthy individuals. 

Lower levels 

The values between 0.3-1.00 mg/ dL are considered low risk and noted in people with mild infections, chronic conditions, smoking, sedentary lifestyles, or pregnant women. These values are also noted in people with obesity, depression, diabetes, periodontitis, gingivitis, and the common cold.

Moderate levels

The levels in the 0.1-10 mg/ dL are considered moderate. This level is a warning sign and alerts the possibility of severe acute or chronic inflammation, malignancies, heart disease, or other issues. 

High levels

The values between 10-50 mg/ dL are markedly higher and indicate an underlying inflammation. Levels above 50 mg/ dL are noted in severe bacterial infections. 

High-sensitivity C-reactive protein (hs-CRP) test: The hs-CRP test determines the risk of developing cardiovascular diseases. The diagnostic standards are;

• Lower risk: less than 1 mg/ L
• Moderate risk: 1-3 mg/ L
• Higher risk: greater than 3 mg/ L. 

The CRP test is normally performed only after being asked by the doctor. Its values vary regularly, so another test after a few weeks is recommended. If you have a high risk of cardiovascular disease, the doctor can ask you to undergo regular testing.

7. Cardiac Biomarkers

Cardiac biomarkers are released wherever there is damage to the heart muscles, e.g., during a heart attack, stroke, ischemic injury, acute myocardial infarction, coronary artery disease, etc. These biomarkers help the doctor or cardiologist diagnose and monitor heart disease and predict the outcome of an adverse cardiac health event. The testing of these biomarkers is helpful for;

• Diagnosis of the nature and extent of cardiac injury.
• Diagnosis of the condition in case of symptoms, e.g., chest pain, angina, profuse sweating, breadth shortness, etc. 
• Monitoring of the success or failure of the cardiac treatment regime. 

The common biomarkers detected in response to a cardiovascular event and their diagnostic thresholds are;

Troponin: This biomarker is released immediately after the cardiac injury within hours, and the elevated levels persist for up to 2 weeks. The rising level in successive tests is a sign to worry. The diagnostic criteria for troponin are;

• It should be between 0-0.04 ng/mL in normal people. In the case of high-sensitivity cardiac troponin (hs-cTn), the values should be less than 14 ng/ L.
• A higher level indicates heart injury. If the results are normal after 12 hours of the start of symptoms, e.g., chest pain, the symptoms are unlikely due to the heart attack. 

High sensitivity troponin: Also known as hs-troponin, this test is designed to detect much lower troponin levels and can help diagnose a cardiac event much earlier. All labs may not have the facility to test it, and it can be positive in people without any symptoms and can indicate a high risk of cardiovascular disease. It can detect very small troponin values (in nanograms per litre).

Creatinine kinase (CK): Another version of this test is the CK-MB (creatinine kinase-myocardial band)  test. This enzyme is present in the heart tissues, and its levels are elevated in case of a heart injury. It's also used to detect a second attack after the first one. The diagnostic criteria for CK are;

• Men: 55-170 U/ L
• Women: 30-145 U/ L
• The values of CK-MB should be 3-5% of all CK, i.e., between 5-25 U/ L. 

Myoglobin: Myoglobin is a muscle protein, and its levels also increase in case of muscle damage. As it could be elevated in case of damage to any muscle, it's not a specific cardiac health biomarker. However, its higher levels in the presence of signs and symptoms could be a sign of heart injury. 

Ischemic modified albumin (IMA): The supply of oxygen to the body is reduced in case of any cardiac health event leading to the production of IMA. Its presence, in combination with the ECG, can confirm a heart injury. 

Heart-specific peptides: Some peptides, e.g., atrial natriuretic peptides (ANP) of any type (A, B or C) and the NT-proBNP (N-terminal proBNP), etc., can also be useful. These peptides are, however, newly discovered, and research on them is ongoing to establish their diagnostic and prognostic worth.

Other biomarkers: Some other biomarkers, e.g., C-Reactive protein, soluble CD40 ligand, or homocysteine, are also released, and their levels are elevated during adverse cardiac health events. Although non-specific, their presence can indicate the possibility of cardiac inflammation. 

The testing for cardiac biomarkers should be included in routine yearly health screening programs after 40-45 years or more early if you have cardiac health risk factors. The doctor may test more specific biomarkers during treatment.

8. Coagulation Panel

Coagulation Panel detects the presence and levels of coagulation factors. The coagulation factors are the proteins that regulate blood coagulation which helps stop bleeding in case of any injury. These tests are recommended to observe the deficiency or total missing of one or more of the clotting factors or defective clotting factors. The liver synthesises these factors, so issues with these factors could signal an issue with liver health. Like deficiency, the excess of one or more clotting factors is equally bad as it can cause internal clot formation, leading to severe consequences. The doctors can also ask these tests for patients who are using blood thinners, have a family history of clotting issues, have immune disorders, or cancers, have undergone or are going for blood transfusion and donation, have vitamin K deficiency or are suffering from severe liver diseases. The tests in this category and their normal values are;

Platelet count: Platelets are the blood cells engaged in clotting, and their deficiency or excess is linked to clotting disorders. The normal platelet count in healthy adults should be 140,000-450,000 cells/ microliters of blood. The counts below 10,000 cells/ul can cause internal bleeding and death. 

Prothrombin time (PT): Prothrombin is the liver protein involved in clotting. Prothrombin time measures the time the blood takes to clot. The normal time is 10-13 seconds. However, the doctor will interpret the results with other factors, e.g., the use of blood thinners, malnutrition, dehydration, liver diseases, haemophilia, etc. Other variants of this test are the activated partial thromboplastin time (aPTT) and thrombin time.

Fibrinogen concentration:  Fibrinogen is another liver protein engaged in clotting. The fibrinogen test (also known as the hypofibrinogenemia test or factor 1 test) measures the level of this protein. The normal fibrinogen level should be 200-450 mg/ dL. A decrease in the fibrinogen concentration due to liver diseases can disturb clotting functions. 

Factor V test: Factor V is also a coagulation factor produced by the liver, and its level is increased in the case of liver and coagulation diseases. The results are given in percentages. So, a 100% result means the level is adequate, a value between 20-70% indicates a mild decrease and a value below 20% means severe deficiency. However, the use of this test is debatable. 

The doctor should decide the frequency of testing according to the clinical need. For example, if a patient is undergoing treatment for clotting issues, daily testing will be needed to see the testing progress. However, yearly testing is enough for screening purposes.

9. Blood Clotting Tests

Blood clotting tests diagnose and monitor the blood clotting disorders that cause the blood coagulation ability to increase or decrease. The liver produces the clotting factors, so if the liver is not working properly or in case of some genetic issues, the clotting factors can be missing, leading to clotting problems. To diagnose the clotting issues as mentioned previously in the clotting panel section. Some other tests which can help the physician are;

Activated partial thromboplastin time ratio (APTR): This test measures the time the thromboplastin uses to change into thrombin. Thrombin is the enzyme that converts fibrinogen into fibrin and clots the blood. The normal values are variable and depend upon the technique and equipment used. The doctor will interpret the test results. 

The tests to diagnose genetic coagulation disorders: The genes of coagulation factors are inherited. The mutations in these genes can be a cause of the clotting disorder. So, the following tests can be helpful for this purpose;

• Factor V Leiden test, which detects the mutations in the DNA responsible for the abnormal production of factor V
• Tests to check mutations in the prothrombin gene (G20210A) 
• Activated protein C resistance test (APCR test)
• Activity tests for proteins C and S. 
• Homocysteine test

Only a geneticist can interpret the test results and can give advice. 

The doctor or haematologist can recommend tests as and if necessary to diagnose the causes of clotting problems. However, these tests can be included in yearly health monitoring programs to screen for any acquired causes. Genetic tests are needed only once in life. Before marriage, tests of both partners are recommended to establish the likelihood that these issues will appear in the children. 

10. Sexually Transmitted Infection Tests

Sexually transmitted infections (STIs) are diagnosed through swab samples from the genital area. This practice can be uneasy for some people. Blood tests are valuable tools for detecting some STIs with reasonable accuracy. To increase the accuracy, the results of these tests are combined with the clinical signs and symptoms. Some STIs which are diagnosed through blood tests are;

HIV

It is diagnosed through blood tests designed to detect the viral antigens and the antibodies produced in response to these antigens. The HIV blood testing kits are easy to perform, and the bands' appearance would help diagnose the condition. Various rapid HIV testing kits are available, which need a blood, urine, or saliva sample and give results within 10-15 minutes. Welzo.com offers an HIV test kit that detects the HIV 1 & 2 antibodies and P24 antigens. The results are provided in 2 days. Click here to get your test kit. 

Genital herpes

Blood tests confirm herpes if symptoms are apparent or the person has an infected partner. These blood tests also detect the viral antigens or antibodies against them in the blood. However, a positive test can only be obtained after an incubation period of 12 days, during which the viral infection needs to establish itself. Sometimes, antibodies can be lowered, and the patient can have a negative test even with the signs of disease. Two positive tests at separate intervals are needed to confirm the infection. 

Hepatitis B

Multiple blood tests are also available for hepatitis B. These tests also detect viral antigens (e.g., surface antigen HBsAg) and antibodies (e.g., core antibody HBcAb, and the surface antibody (HBsAb). The antigen tests will tell the doctor if the person is infected and contagious, and the antibody test will help him assess the immune response status.  

Syphilis 

Several different blood tests are available to diagnose syphilis. These are;

Treponemal tests: These tests detect the antibodies in the blood of patients. Two separate tests at separate intervals are needed to confirm the infection.  

Nontreponemal tests: These tests detect and quantify the antibodies and help diagnose the stage of disease and assess if the treatment is successful.

Blood cultures

Some germs can colonise the blood and be detected through bacterial cultures. These tests are, however, time-consuming and need sophisticated labs with qualified staff. 

PCR tests

These tests are the most accurate ones and detect bacterial or viral genomes. They also need advanced facilities.  

The frequency of screening depends upon many factors. However, people in their reproductive years should go for screening for STIs at least once a year. After reproductive life, the testing becomes unnecessary except for monitoring already present infections.

If you have or suspect any STI, the All in One STI Test kit offered by Welzo.com can be really helpful. It just needs a single blood sample to provide accurate results quickly. Click here to visit the page. 

11. Dhea-Sulfate Serum Test

This test quantifies the DHEA in the blood. DHEA means dehydroepiandrosterone sulfate. It is primarily a male hormone, but it is found in both genders. The adrenal gland produces this hormone, and a small amount (10%) is also made inside the ovaries in females and testes in males. The inadequate level could mean any issue with these organs. This hormone is involved in the functioning of ovaries and testicles and the development of male sexual characteristics. This test is used to assess the health of the adrenal gland, diagnose the issues with ovaries and testicles, understand the causes of delayed or early puberty, and find out the reasons for the development of male characteristics in females. 

The normal level of DHEA is a function of age. The reference values are measured in micrograms per deciliters (μl/ dL), and their values depend upon age and gender. The reference values are summarised in the table below;

Age	Men (μl/ dL)	Women (μl/ dL)
0-30 days	Not established	Not established
1-12 months	4.8-64.1	4.8-64.1
1-4 years	0.1-56.4	1.8-97.2
5-8 years	18.0-194.0	26.1-141.9
9-11 years	49.5-270.5	35.0.192.6
12-14 years	49.5-270.5	67.8-328.6
15-19 years	115.3-459.6	110.0-433.2
20-24 years	164.3-530.5	110.0-431.7
25-34 years	138.5-475.2	84.8-378.0
35-44 years	102.6-416.3	57.3-279.2
45-54 years	71.6-375.4	41.2-243.7
55-64 years	48.9-344.2	29.4-220.5
65-74 years	30.9-295.6	20.4-186.6
75 years or more	20.8-226.4	13.9-142.8

The high DHEA indicate;

• Polycystic ovarian syndrome (PCOS)
• Tumours of adrenal gland
• Adrenal hyperplasia
• Ovarian cancer

The low DHEA indicate;

• Pituitary adenomas
• Addison’s disease 

This test is optional. It is often recommended for any fertility issue.

12. Blood Enzyme Tests

Enzymes are the proteins that catalyse the reactions inside the body; e.g., digestive enzymes help digest food. Blood enzyme tests are used to analyse the enzymes in the body and diagnose the deficiency of enzymes and the inherited or acquired conditions responsible for the enzyme deficiency. Some other enzymes provide information about the functions of various body organs, e.g., the levels of some cardiac enzymes are elevated after an adverse cardiac health event, and higher levels of liver enzymes indicate liver injury. 

Many tests are available that target different organs. Some of them are;

Creatine phosphokinase isoenzyme (CPK): This test measures the level of CPK in blood. The CPK enzymes are present in the skeletal muscles, heart, and brain; their levels depend on gender and age. This test helps the physician diagnose a heart attack and estimate the damage to the heart tissues. For reference purposes, the total CPK level in blood should be 34-145 U/ L for women and 46-171 U/ L for men. 

More specifically, three types of CPKs are tested.

CPK-1: It's mostly associated with the lungs and brain, and its levels are elevated due to brain injury, brain cancer, injury to the lung tissues, seizures, etc. 

CPK-2: It is associated with the heart, and its levels are elevated due to cardiac arrest, heart injuries, defibrillation, electrical injuries, inflammation of cardiac muscles, open heart surgery, etc. 

CPK-3: It is associated with muscles, and its levels are disturbed due to recent surgeries, seizures,  heavy exercises, muscular dystrophy, intramuscular injections, inflammation of muscles, etc. 

The enzyme tests associated with the heart, liver, and digestive systems are mentioned in the sections above. These tests are not part of a routine health monitoring program, but the healthcare provider can ask you to go for testing to confirm the cause of specific symptoms.

When to Get a Blood Test?

A person should get a blood test whenever the doctor recommends it. The doctors recommend that patients undergo blood testing at least once a year. This testing should be done in combination with the other tests. This practice will allow the practitioners to screen and monitor health conditions earlier. This recommendation is for the people who regularly attend a clinic. 

For people above 40 or those living with chronic conditions, the testing frequency can be increased, and a new test is often required at each bi-yearly or quarterly visit to the clinic. The same rule applies to people experiencing unusual symptoms, e.g., weight gain or loss, nail and skin abnormalities and unusual fatigue. The doctor can ask for a new test for additional screening for the following purposes;

• For making advice about lifestyle changes and diet switching
• Prescribing dietary supplements
• Making advice about an exercise plan. 

Besides this routine blood work, blood testing can be required in some emergencies, e.g., for blood donation, blood transfusion, before or during a surgical procedure etc. 

How Often Should Blood Test Be Taken?

The blood tests should be conducted yearly for high-risk people and 2-3 years apart for all people. A detailed answer is provided in the "When to get a blood test" section. However, the general physician has the ultimate authority to recommend the testing frequency. The testing frequency depends upon the purpose of testing too. The following study can give the readers a hint about testing frequency.

Where to Get a Blood Test?

Blood testing facilities are offered by almost all diagnostic laboratories. If a blood test is prescribed,  visit the nearest diagnostic lab and consult the pathologist. Welzo offers many solutions for people who want blood testing. Besides offering a diverse variety of blood tests, it also maintains high-tech labs for its clients. 

How to Prepare for A Blood Test?

There are certain preparations needed for having a blood test. These are;

1. Prepare yourself mentally for the test by stabilising and minimising the stress, recognising and addressing your fears, e.g., needle phobia etc. Ask the laboratory staff to use local anaesthetic preparations if the procedure is expected to be very painful. 
2. Understand the details of the procedure and know well how it works. Be plain to the laboratory staff about everything and ask anything if needed.
3. Use stress-reducing techniques, e.g., deep breathing, accepting anxiety and practising positive self-talk.
4. Avoid drinking or eating except simple water at least 12 hours before the test. The doctor will instruct whether a non-fasting or fasting test is required. The blood tests that need fasting are blood glucose, iron level test, lipid profile etc., and are often conducted early before breakfast.
5. Drinking too much water can dilute the blood and influence some tests e.g., haematocrit. Ask the pathologist for more specific instructions.
6. If the person uses some medications, he/she should consult the doctor about whether to continue using them or avoid them. If the test is recommended to check the efficacy of treatment, you will need to carry on with them. However, the following drugs can impact the results of blood tests;

○ Steroids (e.g., prednisolone, betamethasone etc.) can increase the levels of triglycerides and cholesterols.

○  Beta-blockers can increase triglycerides and decrease LDL cholesterol.

○ Antipsychotics and antidepressants can cause a false positive result in blood pregnancy testing.

○  Some antibiotics, e.g., penicillin, can influence blood glucose levels

○ Erythromycin and cotrimoxazole can influence blood clotting, and ofloxacin and levofloxacin can influence renal functions.

○ Herbal medicines and vitamin supplements can influence the results of liver tests.

1. Some hormonal tests, e.g., renin, aldosterone and cortisol, are influenced by exercise. The patient must avoid eating and drinking, avoid any type of exercise and lie down calmly for at least 30 minutes before taking the blood sample.
2. Refrain from some activities that can influence the outcome of tests, e.g., sex, smoking, exercise, dehydration etc., which can influence the results of tests for reproductive hormones.
3. Be careful about the time, as the results of some tests, e.g., the progesterone and oestrogen tests, are time specific and can change from time to time.
4. Drink plenty of fresh water. Drinking sufficient water increases the blood volume and inflates the blood vessels, making it easy for the lab technician to collect the blood. It also improves blood flow. However, some tests, e.g., pregnancy test results, are influenced by drinking excessive water, which also causes the urine to become dilute.
5. Warm the sampling area, e.g., by wearing warmer clothes or using hot compresses. It will increase the blood flow in the area, facilitating blood flow.
6. Inform the laboratory staff if you are allergic to latex or any other materials used for blood collection. 

What Takes Place During a Blood Test?

During a blood test, the laboratory staff collects the blood sample and dispatches it to the processing section. In this section, the sample is processed and the results are generated. The results are sent to the pathologist who reviews them and signs the reports. All the patients have to do is cooperate with them and inform them about any issues. The blood test starts with taking a sample from the veins in the arm or hand. The arm is more convenient because it can easily be accessed and has prominent veins. Sometimes, the technicians use a tourniquet to facilitate the sampling. The veins near the elbow and wrist are more prominent. In the case of children, the blood samples are taken from the back of the hand, and to reduce the pain, some numbing agent or local anaesthesia is often used. 

Before taking the sample, the attendant or technician uses antiseptic wipes to clean and disinfect the area. If he/she misses, the patient should be reminded to avoid infection risk. The needle attached to a special container or syringe is gently pushed into the vein. A slight scratching or pricking sensation can be felt at the site, which can be slightly painful, but it is nothing to be worried about. The syringe draws the blood sample into the collection tube. If the process is painful, inform the doctor or attendant. 

After taking the sample, the tourniquet should be removed immediately, and the needle removed. The patient should apply gentle pressure at the collection site using a sterile cotton pad for a few minutes. It will help in healing the wound. If the wound is larger, a small plaster can be placed over it.

After blood collection, the samples are stored and dispatched in a strict cold chain to the concerned labs. The procedure of sampling and storage is simple if carried out correctly. Inside the laboratory, the samples will be processed. In the laboratory, a professional staff of biomedical scientists will handle and analyse the samples. These professionals use various techniques and equipment to process the samples and produce the results. 

In the laboratory, the pieces are divided into two groups;

• Group 1: In this group, the details will be analysed for CBC. A small amount of mixed anticoagulant blood is placed in the blood count analyser. This machine uses a light beam to count the cell types, estimate Haemoglobin and other CBC parameters, and generate results. Group 2: The samples in this group are intended to be used for biochemical analysis. For this purpose, the blood samples are processed in a centrifuge to isolate the cells and serum. These serum samples are analysed using diagnostic kits and machines, and results are compiled. The technology used in a biochemical lab is very advanced. However, it can't be used correctly if the experts are there to operate it and interpret the results. 

The reports are analysed and signed by a pathologist and then dispatched to the hospital or GP. Quality control, documentation and proper management are ensured during this process.

What happens after the blood test?

After the blood test, the finalised reports are dispatched to the concerned physician.. Some labs also provide online access to the reports. The patients can download these reports and take them to the general physician or the specialist. The concerned doctor will review the reports and will combine the results of lab reports with the clinical signs and symptoms to arrive at a definitive diagnosis. The doctor will write a prescription which will be sent to the pharmacy. The patients should use the medicines as prescribed and consult the doctor again after the end of the course. In no case should the patients engage in self-interpretation and self-medication as it can result in patients taking unnecessary drugs with potentially dangerous consequences.

Some healthcare providers (e.g., Welzo) provide online consultation services to clients which allow the patients to get everything in the comfort of their homes. Click here to visit Welzo and see what it is offering for healthcare.

How Long Does It Take to Get the Blood Test Result?

Blood test results take a few hours to weeks to be ready. The exact timing depends upon the tests being conducted. The samples intended for blood tests like blood grouping, CBC etc. are processed immediately, and the results are available on the same day. Other tests, e.g., biochemical parameters and PCR, take some time and the results of some tests, e.g., culture, take days to weeks. New diagnostic techniques are rapidly developing which allow much faster testing. The results of some tests, e.g., HbA1c, vitamin D blood test, coeliac blood test, rheumatoid arthritis blood test etc., take longer to work and can take weeks. So, be patient and keep yourself calm. 

Irrespective of the time taken for the test, self-interpretation should be avoided as many factors are to be considered while interpreting the results. Irresponsible self-interpretations can cause unnecessary frustration and worries.

How important is Blood Test to improve a Person's General Health?

Undergoing annual blood screening is very important to monitor, treat and prevent various types of degenerative diseases. Blood testing provides a snapshot of a person's general health and helps the doctor to diagnose and monitor the diseases well before they become too advanced to be handled. So, regular blood testing is often practised even if a person is completely healthy. There are many benefits of routine blood testing.

They provide reliable data and trustable measures to track overall wellness and health. The number of blood cells is changed in response to any stresses e.g., infections. Also, any problem in the body leaves some signature marks in the blood too. They help in disease diagnosis. Although the markers of all diseases are not present in the blood, blood testing can still be very helpful. The recent advances in medicine are able to find biomarkers in blood against various new diseases and the quest for these markers is continuing and is expected to provide more in-depth information. Blood testing provides an insight into the metabolism and various chemical reactions within the body and helps to monitor and prevent metabolic diseases, e.g., diabetes, obesity, hypercholesterolemia etc. 

The liver is the centre of metabolism. It's a major detoxification house and performs a variety of functions. Liver diseases seldom show any signs until the situation has advanced too far. Once the signs become clear, most of the liver tissue is already lost. The blood tests allow you to monitor liver health. Various blood tests, e.g., BUN, creatinine, mineral levels, etc., allow monitoring of the health of kidneys. Blood tests allow the monitoring of different hormones and enzymes, e.g., oestrogen, progesterone, estradiol, DHEA etc., in the body, which have various functions. Some of these hormones influence reproduction and the menstrual cycle. So, blood tests can be helpful in diagnosing reproductive health issues. Blood testing allows physicians to access the health of the immune system by quantifying the antibodies produced in response to infections and vaccinations.

In short, blood testing is a touchstone for overall health. Frequent blood testing allows people to be proactive about their health and provides access to various biomarkers related to overall health.

How important is Blood Test to a Person's Sexual Health?

“Sexual health means a state of physical, mental, emotional and social well-being about sexuality”. Optimum sexual health is not just related to physical health, it is also influenced by psychological factors. So, sexual health just doesn’t mean the absence of sexual diseases. The only way to achieve optimum sexual health is to identify various problems which can compromise sexual health in time. The blood tests important for sexual health are the SHBG test, blood tests for sexually transmitted diseases and blood hormone tests.

Erectile dysfunction is the inability to achieve or maintain an erection long enough to allow successful sexual intercourse. Blood tests are helpful to diagnose erectile dysfunction, but not directly. ED is not a disease whose causative agent can be detected in the blood. It is a multifactorial issue, and many factors have a role. Some factors are; low levels of hormones, particularly testosterone, psychological Depression, diabetes (type 2), blood vessels and heart diseases, hypertension, chronic kidney diseases, injuries, cancers in the reproductive organs, atherosclerosis etc.

Blood tests help to diagnose these causes and help the doctor to make a treatment plan and monitor the efficacy of treatment. However, the treatment of ED needs a broader approach. 

How important is Blood Test to a Person's Mental Health?

Mental health is related to the internal state of mind and has some connection to physiology. Hence, blood tests are of limited value for screening mental health. Mental health means a state of mental well-being that allows a person to work well, cope with the regular stresses of life, learn well, realise his/her abilities and contribute positively to the environment. 

Compromised mental health results in the release of many biomarkers in the body. It is also a sign of vitamin and mineral deficiencies. So, blood tests can give some help. Some blood tests that help to diagnose depression are; the c-reactive protein test, vitamin D blood test, thyroid panel, mineral tests, vitamin B12 test, and oestrogen and progesterone blood tests. 

Does Blood Testing Have Risks?

Yes, blood testing exposes you to some health risks just like any other biological process. These risks are minimised by following proper protocols related to the collection and processing of blood samples. Most blood tests need just a small amount (3-5ml), and the patient is not expected to experience any mild or severe issues after testing. If this happens, the infirm informs the doctor or anyone taking the test and get their aid to tackle it. 

However, some risks are possible e.g., the;

Infection at the wound site:. In rare cases, the sample collection site can get infected, causing redness, swelling and pain. Remember that hospital is a site where dangerous germs are present. So, the person can get these nosocomial infections. In these cases, immediately seek medical assistance. 

Haematoma: Haematoma means the collection of clotted blood at the site of sample collection under the skin. It happens when bleeding occurs under the skin, and blood clots form a lumpy mass. It can also happen if the tourniquet is not opened timely. It will resolve spontaneously without any pain. However, ice packs can be used to ease the swelling. In case it persists, seek medical assistance. 

Excessive bleeding: The wound, in most cases, is very small, and the bleeding stops immediately. However, if (due to bleeding disorders), the bleeding doesn't stop, inform the doctor as excessive blood loss can be very risky. 

Heavy bruises: The needle will leave a small bruise or wound at the sampling site, which should not be a source of worry and fades away within days. In rare cases, serious bruises may develop at the site of the needle prick. Bruises are particularly experienced if the pressure (with a cotton pad) is not applied to stem the blood flow. The local damage to the vein during needle insertion can also be a cause. It shouldn't be a source of worry, and it should heal with mild care. Otherwise, ask the doctor for help as it can lead to the development of potentially dangerous phlebitis (inflammation of the local vein).

Dizziness and fainting: Some people feel dizziness and weakness after the blood collection. These symptoms show a drop in blood pressure. It is particularly experienced by people who are fearful of blood or needles. In case of this issue or if it is expected, the patients need to inform the laboratory staff about it and follow their recommendations.