Glucose Blood Test

What’s covered?

A glucose blood test is a simple way to check your blood sugar level. This type of test measures the amount of glucose in a sample of your blood. Glucose is a kind of sugar that comes from carbohydrates in the foods you eat and provides energy for the cells throughout your body to function properly. You need enough glucose in your blood, but too much can cause serious health problems.

If you have diabetes, keeping track of your blood sugar level can help you control the condition and prevent complications like nerve damage and heart disease. Your doctor may ask you to do a glucose blood test periodically throughout the day or as part of an annual wellness exam to check for signs of diabetes or other conditions that affect how well your body handles glucose. If you would like more details, visit our comprehensive guide to blood testing here.

The glucose blood test doesn't require any special preparation beforehand, and you can easily get it during a regular office visit. Depending on the results of your test, your doctor might recommend other tests or lifestyle changes to help manage your diabetes or prevent related complications.

What Is a Glucose Blood Test?

A glucose blood test measures the amount of glucose (also called sugar) in your blood. Your body gets energy from the food you eat by breaking it down into different components. Glucose is one of these components, and the cells throughout your body are able to use it as an energy source. When you have diabetes, your body either can't produce enough insulin or can't use its own insulin as well as it should to help regulate the amount of sugar in your bloodstream. This causes a buildup of glucose that can lead to serious health problems over time if left untreated.

Glucose tests are also used for other conditions that affect how well your body handles glucose, including pregnancy, liver disease, and hypoglycemia.

Why Is a Glucose Blood Test Done?

A glucose blood test is done as part of a regular physical exam or to monitor your diabetes management plan. Your doctor might do the test to screen for type 1 or type 2 diabetes (or both) if you have risk factors such as obesity (especially if you don't exercise), family history of diabetes, high cholesterol levels, or other health conditions. Other risk factors can include age over 45, being African-American, Asian-American, Pacific Islander American, Hispanic/Latino American or Native American and having had gestational diabetes during pregnancy. If you're pregnant and are at high risk for developing gestational diabetes, you may also have a glucose blood test.

The results of your glucose blood test can help your doctor determine whether you have either type 1 or type 2 diabetes, monitor your treatment plan if you do have diabetes, or detect the condition before symptoms develop. A high result on a random glucose test taken at any time during the day may suggest that you have diabetes, but doing additional tests will confirm the diagnosis and rule out other conditions that might be causing similar symptoms. Your doctor might also perform special test to help diagnose gestational diabetes (a form of diabetes that develops during pregnancy).

Your doctor may recommend regular testing later if you're diagnosed with type 1 or type 2 diabetes to make sure your levels remain within normal range as part of routine diabetes management.

What Does a Glucose Blood Test Involve?

The test involves having your doctor or nurse draw a small amount of blood from your arm using a device called a lancet, which looks similar to a large hypodermic needle. A drop of the blood is put onto test strips, which are then placed in the glucose meter. The meter gives the result within seconds, and you'll get your results on paper or on an electronic display screen. You might be able to get these results immediately if you take them home to do yourself. If not, your doctor will send the sample out for analysis at a lab and let you know when they're available again.

You can expect to feel only mild pressure when the lancet punctures your skin, and the process usually only takes a few minutes from start to finish. If you're not able to do the test yourself, it's usually quick and easy for someone else as well. It doesn't require special preparation beforehand or cause any discomfort during or afterward (though you may have a little bruising if you're prone to that).

If you take your results home with you, be sure not to eat anything before doing them unless your doctor says otherwise – eating can affect your glucose levels and make it difficult to get accurate results. Avoid strenuous activities beforehand too; they can also raise your blood sugar temporarily, which will make getting an accurate reading more challenging. Drinking alcohol before testing might also cause an inaccurate result.

Results of a Glucose Blood Test

A normal fasting glucose (a test taken first thing in the morning) is between 70 and 100 milligrams per deciliter (mg/dL). When it's taken at any other time during the day, your blood sugar level should be higher – between 100 and 140 mg/dL. A value over 200 on a random or post-meal test can indicate diabetes, but you'll need to do another test for confirmation. If you're pregnant, you need a blood sugar level under 130 or 135 (depending on which trimester you're in) to avoid developing gestational diabetes. It's also considered abnormal if your body doesn't produce enough insulin or if your body becomes resistant to the insulin it does produce.

Your doctor might also order a hemoglobin A1c test, a more comprehensive blood sugar level measure that can help diagnose diabetes over time and provide information about how well you're managing your condition. Your results show where your average blood sugar levels have been over the three months leading up to the test. The lower they are – ideally between 7 percent and 8 percent – the better control you're keeping on your diabetes. A higher result indicates that your glucose levels aren't as tightly controlled, but it can depend on what stage of diabetes you're in (early or later), any additional conditions you have, whether you're currently being treated for hyperglycemia or hypoglycemia (or both), and more.

Because a glucose blood test is an important tool in early diagnosis, it's important to get the results as soon as possible to begin treatment if you're positive. A delay in diagnosis and treatment can make your symptoms (especially those of diuretic) worse or even lead to long-term complications like early death, heart disease, kidney damage, nerve damage (to the feet or hands), and vision loss. If you have diabetes, it's also essential that you follow the advice of your doctor or other healthcare professional for monitoring your condition so that – with regular glucose tests – you keep your levels under control and prevent further health issues from developing.