Which Blood Markers Reflect Gut Health?

Medically reviewed and written by Dr Zeeshan Afzal, MBBS — Medical Content Lead, Welzo. Last reviewed: August 2026.

A gut health blood test is one of the most common starting points when digestive symptoms will not settle. It cannot see your microbiome directly, but it can reveal inflammation, malabsorption, coeliac autoimmunity, anaemia and liver or pancreatic involvement — the downstream consequences of a gut that is not working properly. If you have been searching for which blood markers reflect gut health, this guide explains exactly what each marker measures, what abnormal results usually mean, and where blood testing fits alongside stool testing, breath testing and microbiome sequencing. For broader background before you read on, our complete guide to gut health in the UK covers the fundamentals, and you can browse the full Welzo gut health range and our clinically formulated probiotics collection for evidence-informed support. Targeted options include Akkermansia muciniphila for mucus-layer support, modified citrus pectin powder as a gentle soluble fibre, Welzo Ultra Purity Berberine for metabolic and microbial balance, and Welzo Ultra Purity TUDCA for bile flow and liver support. If your concern is specifically inflammation or coeliac screening, see our dedicated guides to the calprotectin test, the coeliac blood test and the zonulin test.

This article is for general information and does not replace personalised medical advice. Blood results must be interpreted by a qualified clinician who knows your history. If you have red flag symptoms — unexplained weight loss, rectal bleeding, persistent vomiting, a change in bowel habit lasting more than six weeks, or difficulty swallowing — contact your GP promptly.

Table of Contents

• What Does a Gut Health Blood Test Actually Measure?
• The Five Groups of Blood Markers That Reflect Gut Health
• Group 1: Inflammatory Markers
• Group 2: Nutrient and Absorption Markers
• Group 3: Immune and Coeliac Markers
• Group 4: Metabolic Markers
• Group 5: Liver, Pancreas and General Chemistry
• Gut Health Blood Test Reference Table
• Markers Sold as "Gut Tests" That Are Not Validated
• What a Gut Health Blood Test Cannot Tell You
• Blood Tests vs Stool, Breath and Microbiome Tests
• How Specific Gut Conditions Show Up in Blood Results
• Red Flags: When Results Need Urgent Assessment
• How to Prepare for a Gut Health Blood Test
• How to Interpret Your Results Sensibly
• What to Do After Your Results
• Frequently Asked Questions
• References

What Does a Gut Health Blood Test Actually Measure?

The phrase "gut health blood test" is used loosely by laboratories and wellness companies, and that vagueness causes a lot of confusion. There is no single blood test that measures the health of your gut. What exists instead is a panel of individual markers, each of which measures something specific about the body, and each of which can be influenced by what is happening in the digestive tract.

Blood is downstream of the gut. Everything you absorb crosses the intestinal lining and enters the portal circulation before reaching the rest of the body. When absorption fails, blood levels of iron, vitamin B12, folate and fat-soluble vitamins fall. When the intestinal lining is inflamed, immune proteins and acute-phase reactants rise. When the liver or pancreas is involved, enzymes leak into the circulation. Blood testing reads these signals, and reads them reliably — but always at one remove from the gut itself.

This is a genuinely useful distinction. If you want to know whether your gut wall is inflamed, a blood test gives an indirect clue and a stool calprotectin gives a much closer answer. If you want to know whether your gut is absorbing nutrients, blood is the definitive test. Understanding which question you are asking determines which test you should have.

Who Should Consider a Gut Health Blood Test?

• Persistent bloating, abdominal pain or altered bowel habit lasting more than four to six weeks
• Unexplained fatigue alongside digestive symptoms
• Suspected coeliac disease or gluten intolerance
• A family history of inflammatory bowel disease or coeliac disease
• Symptoms of gut dysbiosis that have not responded to dietary change
• Long-term use of medication that affects the gut, such as omeprazole, metformin or non-steroidal anti-inflammatories
• Monitoring a known condition such as Crohn's disease, ulcerative colitis or coeliac disease

The Five Groups of Blood Markers That Reflect Gut Health

Clinically, the markers worth measuring fall into five groups. Ordering all of them is rarely necessary; a good clinician selects based on symptoms.

Group 1: Inflammatory Markers

Inflammatory markers are the closest blood tests get to detecting active gut disease. They are sensitive but not specific — they rise in inflammation anywhere in the body, from a chest infection to rheumatoid arthritis.

C-Reactive Protein (CRP)

CRP is an acute-phase protein made by the liver in response to inflammatory signalling, principally interleukin-6. It rises within hours of an inflammatory stimulus and falls quickly once the stimulus resolves, which makes it a good real-time marker.

In gastroenterology, CRP is used to flag possible inflammatory bowel disease, diverticulitis, and infective colitis. A normal CRP does not exclude these conditions — a meaningful proportion of people with mild Crohn's disease or ulcerative colitis have a normal CRP — but a persistently raised CRP with digestive symptoms always warrants investigation.

High-Sensitivity CRP (hs-CRP)

hs-CRP detects much lower concentrations and is used mainly for cardiovascular risk stratification. In gut health contexts it is sometimes marketed as a marker of "low-grade inflammation" linked to gut barrier dysfunction. There is a genuine research signal here, but hs-CRP is affected by body weight, smoking, oral contraceptives and recent infection, so an isolated mildly raised value should not be over-interpreted.

Erythrocyte Sedimentation Rate (ESR)

ESR measures how quickly red cells settle in a tube and rises more slowly than CRP, reflecting inflammation over weeks rather than days. It is still routinely used in the workup of anaemia and inflammatory disease. The British Society of Gastroenterology highlights both ESR and CRP in the assessment of iron deficiency anaemia, because inflammation can mask iron deficiency by artificially raising ferritin.

Full Blood Count: White Cells and Platelets

A raised white cell count suggests infection or significant inflammation. A raised platelet count (thrombocytosis) is a frequently overlooked but clinically important finding — it is common in active inflammatory bowel disease and in some gastrointestinal cancers, and in primary care an unexplained raised platelet count is treated as a signal that deserves attention.

Albumin

Albumin is the main protein in blood. It falls in three gut-relevant situations: chronic inflammation (it is a negative acute-phase protein), protein-losing enteropathy where protein leaks through a damaged intestinal lining, and severe malnutrition or malabsorption. A low albumin alongside digestive symptoms is a meaningful abnormality and should never be dismissed.

Group 2: Nutrient and Absorption Markers

This is where blood testing genuinely outperforms every other type of gut test. Nutrient levels are the direct output of small intestinal absorption, and the pattern of deficiency often points to the anatomical site of the problem.

Ferritin and Iron Studies

Iron is absorbed in the duodenum and upper jejunum, so iron deficiency is a classic marker of upper small bowel disease — coeliac disease being the leading example — and of chronic blood loss anywhere in the digestive tract.

The British Society of Gastroenterology guidelines on iron deficiency anaemia note that approximately one third of men and postmenopausal women presenting with iron deficiency anaemia have an underlying pathological abnormality, most commonly in the gastrointestinal tract. That single statistic explains why unexplained iron deficiency in these groups triggers endoscopic investigation rather than simply a course of iron tablets.

The BSG also confirms that serum ferritin is the single most useful marker of iron deficiency anaemia, and that coeliac disease is identified in 3 to 5 per cent of iron deficiency anaemia cases, which is why coeliac serology is part of the standard workup. American Gastroenterological Association guidance summarised by the American Academy of Family Physicians reports that a ferritin threshold below 45 micrograms per litre has approximately 85 per cent sensitivity and 92 per cent specificity for iron deficiency in people who are anaemic.

The Ferritin Trap

Ferritin is also an acute-phase protein, so it rises during inflammation. Someone with active Crohn's disease can be profoundly iron deficient while showing a "normal" ferritin. This is why transferrin saturation, CRP and ESR are measured alongside it. If you are taking iron supplements and struggling with side effects, our guide to iron supplements and constipation covers practical alternatives.

Vitamin B12

Vitamin B12 requires intrinsic factor from the stomach and is absorbed in the terminal ileum. Low B12 therefore points to specific anatomical problems: atrophic gastritis or low stomach acid, pernicious anaemia, long-term proton pump inhibitor or metformin use, terminal ileal Crohn's disease, previous bowel resection, or small intestinal bacterial overgrowth, in which bacteria consume B12 before the host can absorb it.

A raised mean cell volume (MCV) on the full blood count is a supporting clue, though it can be masked when B12 deficiency coexists with iron deficiency, producing a deceptively normal MCV.

Folate

Folate is absorbed in the jejunum. Low folate with normal B12 suggests proximal small bowel disease or poor dietary intake. Interestingly, SIBO can produce the opposite pattern — bacterial folate synthesis can push serum folate up while B12 falls.

Vitamin D

Vitamin D is fat-soluble, so deficiency can indicate fat malabsorption from coeliac disease, pancreatic insufficiency, bile acid problems or extensive small bowel disease. Vitamin D deficiency is extremely common in the UK for reasons entirely unrelated to the gut, so it is only meaningful when read alongside other markers.

Calcium, Magnesium and Zinc

Low calcium and magnesium can reflect malabsorption and, in the case of magnesium, long-term PPI use. Zinc is absorbed in the small intestine and low levels are seen in inflammatory bowel disease and chronic diarrhoea. Magnesium is also relevant in the other direction — many people use magnesium for constipation.

Group 3: Immune and Coeliac Markers

This group contains the only blood tests that come close to being diagnostic for a specific gut condition.

Total IgA and IgA Tissue Transglutaminase (tTG)

NICE guideline NG20 specifies that when clinicians request serological testing for suspected coeliac disease in young people and adults, laboratories should test for total immunoglobulin A and IgA tissue transglutaminase as the first choice, use IgA endomysial antibodies if IgA tTG is weakly positive, and consider IgG-based tests such as IgG EMA, IgG deamidated gliadin peptide or IgG tTG if IgA is deficient.

The reason total IgA is measured alongside tTG is critical: selective IgA deficiency is more common in people with coeliac disease, and if you are IgA deficient, the IgA tTG test will be falsely negative. Missing this is one of the commonest laboratory pitfalls in coeliac testing.

You Must Be Eating Gluten

Coeliac serology only works on a gluten-containing diet. Standard practice, reflected in NIHR evidence synthesis on coeliac diagnosis, is that patients must continue eating gluten daily for at least six weeks before testing. NHS laboratory guidance commonly specifies gluten in more than one meal per day over that period. Starting a gluten-free diet before testing is the single most common reason for a false negative result. NICE is explicit that people should not start a gluten-free diet until the diagnosis is confirmed by a specialist, even if serology is positive.

How Accurate Is Coeliac Serology?

Published diagnostic accuracy data indicate that the tTG-IgA test has a sensitivity in the region of 78 to 100 per cent and a specificity of 90 to 100 per cent in people eating gluten, with performance depending on the degree of intestinal damage and gluten intake. In adults, a positive result usually leads to duodenal biopsy for confirmation rather than immediate lifelong dietary treatment. Our guides to the coeliac test in the UK and gluten intolerance cover this in more detail.

Thyroid Function and Thyroid Antibodies

Thyroid disease is not a gut condition, but it belongs in this panel for two reasons. First, an underactive thyroid causes constipation and an overactive thyroid causes diarrhoea, so thyroid testing rules in or out a common mimic of gut disease. Second, autoimmune thyroid disease clusters with coeliac disease, so finding one raises the index of suspicion for the other.

Group 4: Metabolic Markers

The relationship between the microbiome and metabolic health is one of the most active areas in gastroenterology research. These markers do not diagnose gut disease, but they describe the metabolic environment your gut bacteria live in and contribute to.

HbA1c and Fasting Glucose

HbA1c reflects average blood glucose over roughly three months. There is substantial observational evidence linking microbiome composition and short-chain fatty acid production to glycaemic control, and dietary changes that improve microbiome diversity tend to improve HbA1c as well. Our guide to gut health and blood sugar explores the mechanisms, including the role of short-chain fatty acids.

Lipid Profile

Triglycerides and HDL cholesterol respond strongly to fibre intake and are influenced by bile acid recycling, a process that is entirely dependent on gut bacteria. Soluble fibre lowers LDL cholesterol through bile acid binding, which is covered in our article on fibre and cholesterol. A poor lipid profile in someone with a low fibre intake is, indirectly, a gut signal.

Group 5: Liver, Pancreas and General Chemistry

Liver Function Tests

ALT, AST, ALP, GGT and bilirubin are grouped as liver function tests. They matter for gut health because the liver receives all portal blood from the intestine, and because bile — produced by the liver — is essential for fat digestion.

Raised ALT and GGT are commonly seen in metabolic dysfunction-associated fatty liver disease, which has well-documented associations with microbiome composition. Raised ALP and bilirubin point towards biliary obstruction or cholestasis. Abnormal liver enzymes alongside diarrhoea can also suggest bile acid malabsorption, and anyone considering bile-supportive supplements should read our guide to TUDCA side effects first.

Amylase and Lipase

These pancreatic enzymes rise sharply in acute pancreatitis. Chronic pancreatic insufficiency, by contrast, is better assessed by faecal elastase than by blood tests — an important example of blood testing having a genuine blind spot.

Urea, Electrolytes and Total Protein

Sodium, potassium, urea and creatinine detect dehydration and electrolyte loss from persistent vomiting or diarrhoea. A low potassium with chronic diarrhoea is a clinically significant finding. Total protein and the albumin-to-globulin ratio provide additional information on nutritional status.

Gut Health Blood Test Reference Table

The table below summarises the main markers, what they indicate, and the typical adult reference ranges used by UK laboratories. Reference ranges vary between laboratories, assays and populations — always use the range printed on your own report.

Markers Sold as "Gut Tests" That Are Not Validated

Several blood markers are heavily promoted by direct-to-consumer testing companies. Being honest about their limitations is part of good clinical practice.

Serum Zonulin

Zonulin is marketed as the leaky gut blood test. The underlying biology is real — zonulin regulates intestinal tight junctions — but the commercial assay is a serious problem. Research published in Frontiers in Endocrinology examined a widely used commercial zonulin ELISA and found that it did not detect pre-haptoglobin 2, the protein it is supposed to measure. Using mass spectrometry and Western blot analysis, the authors identified properdin as the most likely protein being captured instead. The study conclusion is that the assay recognises structural analogues rather than zonulin itself.

In practical terms, a zonulin result should not be used to diagnose intestinal permeability or to justify a supplement protocol. Our detailed articles on the zonulin test and on whether leaky gut is real unpack the evidence in full.

Serum LPS and LPS-Binding Protein

Circulating lipopolysaccharide and LPS-binding protein are used as research measures of "metabolic endotoxaemia". They are informative at a population level in studies, but assay standardisation is poor and there are no validated clinical cut-offs for individuals.

IgG Food Intolerance Panels

IgG antibody panels marketed as food intolerance tests are not supported by national allergy and gastroenterology bodies. IgG antibodies to food generally indicate exposure and tolerance, not intolerance. Acting on these results usually leads to unnecessary dietary restriction, which can itself reduce microbiome diversity. See our review of food intolerance tests in the UK.

What a Gut Health Blood Test Cannot Tell You

Being clear about limitations protects you from over-testing and from over-interpreting normal results. A completely normal blood panel does not mean your gut is healthy — it means the specific things measured were within range. Irritable bowel syndrome, for example, is defined by symptoms and by the absence of abnormal test results, and people with severe IBS routinely have perfectly normal bloods. Our guides to IBS types and supplements for IBS address what to do next in that situation.

Blood Tests vs Stool, Breath and Microbiome Tests

Faecal Calprotectin: The Closest Test to Gut Inflammation

Calprotectin is released by neutrophils that migrate into the intestinal lining during inflammation, and it is excreted in stool. NICE diagnostics guidance recommends faecal calprotectin testing as an option to support clinicians with the differential diagnosis of inflammatory bowel disease or irritable bowel syndrome in adults with recent-onset lower gastrointestinal symptoms for whom specialist assessment is being considered, provided cancer is not suspected and appropriate care pathways are in place.

Diagnostic accuracy work published in the Journal of Crohn's and Colitis confirms that distinguishing IBD from functional gastrointestinal disease is difficult on symptoms alone and that calprotectin materially improves that assessment. A cut-off of around 250 micrograms per gram is commonly used to indicate active disease in people already diagnosed with IBD. Our calprotectin test guide explains sampling and interpretation.

Breath Testing

Hydrogen and methane breath tests are used to investigate SIBO and carbohydrate malabsorption. Blood tests cannot substitute for them. See our SIBO test guide and article on lactose intolerance.

Microbiome Sequencing

Stool DNA sequencing describes which bacteria are present. It is genuinely interesting and increasingly useful for dietary guidance, but it is not a diagnostic test and results differ between providers. Our microbiome test comparison and UK microbiome testing guide compare the main options.

Faecal Immunochemical Test (FIT)

FIT detects human haemoglobin in stool and is used both in the NHS bowel cancer screening programme and in symptomatic patients to prioritise investigation. It is a stool test, not a blood test, despite what it detects. More detail is in our bowel cancer screening guide.

How Specific Gut Conditions Show Up in Blood Results

For condition-specific guidance, see our articles on Crohn's disease diet, ulcerative colitis diet, H. pylori and gastritis.

Red Flags: When Results Need Urgent Assessment

Certain combinations of symptoms and blood results should never be managed with supplements or dietary change alone. Contact your GP promptly if you have:

• New iron deficiency anaemia in a man of any age or a postmenopausal woman
• Unexplained weight loss with any abnormal blood result
• Rectal bleeding, or blood mixed with stool
• A persistent change in bowel habit lasting more than six weeks, particularly over the age of 50
• Difficulty or pain on swallowing
• Persistent vomiting
• An unexplained raised platelet count
• A low albumin with digestive symptoms
• An abdominal or rectal mass
• A first-degree relative with bowel cancer or inflammatory bowel disease diagnosed young

UK referral thresholds for suspected cancer are set out in NICE guideline NG12. Our guide on when to see a GP about stomach problems gives practical thresholds.

How to Prepare for a Gut Health Blood Test

Supplements That Interfere With Results

• Biotin at high doses interferes with many immunoassays, including thyroid tests. Most laboratories advise stopping high-dose biotin 48 to 72 hours before testing.
• Iron supplements taken shortly before the test can transiently raise serum iron.
• Vitamin B12 supplements normalise serum B12 without necessarily correcting tissue deficiency.
• Gluten avoidance invalidates coeliac serology.

Always tell the clinician requesting your test what you are taking, including anything from our gut health collection.

How to Interpret Your Results Sensibly

Reference Ranges Are Not Health Ranges

Laboratory reference ranges are usually derived so that around 95 per cent of a healthy reference population falls inside them. That means roughly one in twenty normal people will have a result flagged as abnormal on any given test. Order twenty markers and you should expect at least one to be flagged. This is a statistical artefact, not a diagnosis.

Patterns Matter More Than Single Values

A single borderline value in isolation is rarely meaningful. Low ferritin plus low haemoglobin plus low MCV is a coherent picture of iron deficiency anaemia. Low ferritin alone in a menstruating woman with no symptoms is a much weaker signal.

Trends Beat Snapshots

If you are monitoring a chronic condition, the direction of travel over three to six months is more informative than any single result. Retesting too frequently generates noise rather than insight.

What to Do After Your Results

If your results are normal but symptoms persist, the sensible next steps are dietary and behavioural rather than more testing.

Fibre and Plant Diversity

Increasing plant diversity is the single best-evidenced intervention for microbiome health. Our guides to 30 plants a week, increasing fibre safely and high fibre foods in the UK give practical starting points. Modified citrus pectin powder is a well-tolerated soluble fibre for people who struggle with bulkier options.

Fermented Foods and Probiotics

Fermented foods and targeted probiotic strains have reasonable evidence for specific outcomes. Start with our guides to fermented foods, choosing a probiotic and the best probiotics in the UK, then browse the Welzo probiotics collection. Akkermansia muciniphila is of particular interest for mucus layer integrity and metabolic markers.

Targeted Support

Where blood results point to a specific issue, targeted support may help alongside medical management. Berberine has evidence for glycaemic and lipid markers — read about berberine interactions before starting. TUDCA is used to support bile flow where fat digestion is impaired. For barrier support, see our reviews of supplements for leaky gut, zinc carnosine and butyrate supplements.

Rebuilding After Antibiotics or Illness

If your results follow a course of antibiotics or an infection, see our guides to probiotics after antibiotics, recovering from a stomach bug and the gut reset protocol.

Frequently Asked Questions

Can a blood test detect gut problems?

Yes, but indirectly. Blood tests reliably detect the consequences of gut disease — inflammation, anaemia, nutrient malabsorption, coeliac autoimmunity, and liver or pancreatic involvement. They cannot see the gut lining or the microbiome directly. A stool calprotectin test is closer to a direct measure of intestinal inflammation, and endoscopy remains the definitive way to visualise the gut.

What blood test shows gut inflammation?

CRP and ESR are the main blood markers of inflammation, supported by white cell count, platelet count and albumin. However, a normal CRP does not rule out inflammatory bowel disease, particularly when disease is mild or limited to the colon. Faecal calprotectin is more sensitive for gut-specific inflammation and is recommended by NICE for distinguishing IBD from IBS.

Is there a blood test for leaky gut?

Not a validated one. Serum zonulin is widely marketed for this purpose, but research published in Frontiers in Endocrinology showed that a widely used commercial zonulin ELISA does not detect the protein it claims to measure and most likely captures properdin instead. Zonulin results should not be used to diagnose intestinal permeability or to justify treatment decisions.

Can a blood test detect IBS?

No. IBS is a clinical diagnosis based on symptom patterns, and blood tests in IBS are characteristically normal. Their role is to exclude conditions that mimic IBS — coeliac disease, inflammatory bowel disease, thyroid disease and anaemia. A normal panel in someone with typical symptoms actually supports the diagnosis rather than undermining it.

Which blood test shows poor nutrient absorption?

Ferritin with iron studies, vitamin B12, folate, vitamin D, calcium, magnesium and albumin together give a strong picture of absorption. The pattern is informative: iron deficiency points to the duodenum, folate deficiency to the jejunum, and B12 deficiency to the stomach or terminal ileum.

Do I need to fast before a gut health blood test?

It depends on the panel. Fasting is generally required for lipid profiles and fasting glucose, typically for eight to twelve hours with water permitted. Inflammatory markers, coeliac serology, ferritin, B12 and folate do not require fasting. Follow the specific instructions from the laboratory or clinic that issued your test.

Can a blood test detect SIBO?

No. SIBO is investigated with hydrogen and methane breath testing. Blood tests can provide supportive clues — a low vitamin B12 with a normal or raised folate is a recognised pattern — but they cannot confirm or exclude the condition.

How often should I repeat a gut health blood test?

For most people with stable symptoms, annually is sufficient. If you are correcting a deficiency, retesting after three months allows time for change to be measurable. People with diagnosed inflammatory bowel disease or coeliac disease follow condition-specific monitoring schedules set by their specialist team. Retesting every few weeks generates noise rather than useful information.

Can I get a gut health blood test on the NHS?

Yes, where clinically indicated. A GP can request a full blood count, CRP, ferritin, B12, folate, vitamin D, liver function tests, thyroid function and coeliac serology, along with faecal calprotectin and FIT where appropriate. NHS testing is symptom-led rather than screening-led, so tests are ordered when there is a clinical reason. Private testing offers convenience and broader panels but the same interpretation caveats apply.

My gut health blood test is normal but I still have symptoms — what now?

This is a very common and legitimate situation. Normal results exclude a set of specific diagnoses; they do not mean nothing is wrong. Functional conditions such as IBS, visceral hypersensitivity, bile acid malabsorption, SIBO and food intolerance are all invisible on standard bloods. The next steps are usually a structured dietary approach such as a low FODMAP diet under dietitian supervision, targeted testing such as a breath test or SeHCAT scan, and attention to the gut-brain connection, sleep and stress. Keep your GP involved rather than self-treating indefinitely.

References

1. National Institute for Health and Care Excellence. Coeliac disease: recognition, assessment and management (NG20). https://www.nice.org.uk/guidance/ng20/chapter/recommendations
2. National Institute for Health and Care Excellence. Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel (DG11). https://www.nice.org.uk/guidance/dg11
3. British Society of Gastroenterology. Guidelines for the management of iron deficiency anaemia in adults. https://www.bsg.org.uk/clinical-resource/guidelines-iron-deficiency-anaemia-in-adults
4. Snook J, Bhala N, Beales ILP, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut. 2021;70(11):2030–2051. https://pubmed.ncbi.nlm.nih.gov/34497146/
5. Scheffler L, Crane A, Heyne H, et al. Widely used commercial ELISA does not detect precursor of haptoglobin2, but recognizes properdin as a potential second member of the zonulin family. Front Endocrinol. 2018;9:22. https://pmc.ncbi.nlm.nih.gov/articles/PMC5807381/
6. Scheffler L, et al. PubMed record. https://pubmed.ncbi.nlm.nih.gov/29459849/
7. Kennedy NA, Clark A, Walkden A, et al. Clinical utility and diagnostic accuracy of faecal calprotectin for IBD at first presentation to gastroenterology services in adults aged 16–50 years. J Crohns Colitis. 2015. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4795527/
8. Elwenspoek MMC, et al. Defining the optimum strategy for identifying adults and children with coeliac disease: systematic review and economic modelling. NIHR Journals Library. https://www.ncbi.nlm.nih.gov/books/NBK585925/
9. American Academy of Family Physicians. Iron deficiency anemia: guidelines from the American Gastroenterological Association. Am Fam Physician. 2021;104(2):211–212. https://www.aafp.org/pubs/afp/issues/2021/0800/p211.html
10. National Institute for Health and Care Excellence. Suspected cancer: recognition and referral (NG12). https://www.nice.org.uk/guidance/ng12
11. National Institute for Health and Care Excellence. Irritable bowel syndrome in adults: diagnosis and management (CG61). https://www.nice.org.uk/guidance/cg61
12. NHS. Blood tests. https://www.nhs.uk/conditions/blood-tests/
13. NHS. Coeliac disease. https://www.nhs.uk/conditions/coeliac-disease/
14. NHS. Vitamin B12 or folate deficiency anaemia. https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/
15. NHS. Bowel cancer screening. https://www.nhs.uk/conditions/bowel-cancer-screening/
16. Coeliac UK. Getting diagnosed. https://www.coeliac.org.uk/information-and-support/coeliac-disease/getting-diagnosed/
17. Crohn's & Colitis UK. https://crohnsandcolitis.org.uk/
18. Guts UK Charity. https://gutscharity.org.uk/

About the Author

Dr Zeeshan Afzal, MBBS is a practising doctor and Medical Content Lead at Welzo. He reviews Welzo's digestive health content against current UK guidance from NICE and the British Society of Gastroenterology, and against peer-reviewed literature.

Medical Disclaimer

This article is intended for general education and does not constitute medical advice, diagnosis or treatment. Reference ranges vary between laboratories and populations. Blood results should always be interpreted by a qualified healthcare professional in the context of your symptoms, medical history and medication. Do not start, stop or change any medication or supplement on the basis of this article. If you have concerning symptoms, contact your GP, call NHS 111, or in an emergency call 999.