Blood tests for celiac disease and IBD
For people with celiac disease or inflammatory bowel disease (Crohn's disease or ulcerative colitis), and people being checked for them.
12 tests explainedAI-verified against cited sources. Awaiting expert reviewLast reviewed 2026-10-19
Celiac disease and IBD both affect the gut lining, which can change how well the body absorbs iron, B12, folate and vitamin D. For celiac disease, a tTG-IgA blood test with a total IgA level is the usual first step, and it is meant to be done while still eating gluten. For IBD, a stool test (calprotectin) and a blood test (CRP) help show whether there is active inflammation between scopes. Nutrient tests look for the shortages linked to both conditions.
The tests that matter most
Most important first. Each one links to its full page, where the note for this group sits near the top.
Tissue Transglutaminase (tTG) IgA
ACG uses tTG-IgA as the main first blood test for celiac disease, measured on a regular diet that includes gluten. Once celiac disease is confirmed, it is repeated to see whether the antibody turns negative on a gluten-free diet.
- Usual adult range
- 0–10 U/mL
Immunoglobulin A (IgA)
ACG suggests measuring total IgA at the same time as the first tTG-IgA, if it hasn't been checked before. If IgA is low, ACG uses IgG-based celiac tests instead, such as DGP IgG or tTG IgG.
- Usual adult range
- 61–356 mg/dL
HLA-DQ2 / DQ8 (Celiac Genetics)
ACG notes that a negative result on this gene test rules celiac disease out. It is especially useful for people who went gluten-free before being tested, or when blood tests and biopsy disagree. A positive result means a gluten challenge can be offered.
Calprotectin, Fecal
Calprotectin is a stool marker of gut inflammation. AGA guidance uses it with symptoms to help judge whether Crohn's disease is active, and BSG notes it helps tell IBD apart from irritable bowel syndrome in younger adults with ongoing diarrhea.
Sources: American Gastroenterological Association (2023) and British Society of Gastroenterology (2019)
- Usual adult range
- 0–50 µg/g
C-Reactive Protein (CRP, incl. hs-CRP)
CRP is a blood marker of inflammation. AGA guidance uses it alongside calprotectin and symptoms to help judge Crohn's disease activity. BSG notes that ferritin is harder to read during inflammation, and that zinc and vitamin D can only be read reliably when CRP is low.
Sources: American Gastroenterological Association (2023) and British Society of Gastroenterology (2019)
- Usual adult range
- 0–5 mg/L
Hemoglobin
Anemia is common in both conditions. Unexplained iron deficiency anemia is one of the reasons ACG lists for celiac testing, and in IBD, BSG notes that low iron, B12 or folate can all lie behind anemia.
Sources: American College of Gastroenterology (2023) and British Society of Gastroenterology (2019)
- Men, 16+
- 13–17.7 g/dL
- Women, 16+
- 11.1–15.9 g/dL
Ferritin
Ferritin is the main test for iron stores, but inflammation pushes it up. BSG notes that in IBD with inflammation, a ferritin up to 100 µg/L (the same as 100 ng/mL) may still reflect low iron, and transferrin saturation can help when ferritin is unclear.
- Men, 20–59
- 30–400 ng/mL
- Men, 60+
- 31–409 ng/mL
Vitamin B12 (Cobalamin)
ACG notes that celiac disease can impair absorption of iron, fat-soluble vitamins and potentially B12 and folate. BSG lists B12 among the blood tests for people with IBD who are malnourished or at risk of it.
Sources: American College of Gastroenterology (2023) and British Society of Gastroenterology (2019)
- Usual adult range
- 232–1,245 pg/mL
Folate (Vitamin B9), Serum
Folate is on ACG's list of other tests that may be part of celiac follow-up, and on BSG's list for people with IBD at risk of malnutrition. Low folate is one of the other causes of anemia BSG asks clinicians to consider in IBD.
Sources: American College of Gastroenterology (2023) and British Society of Gastroenterology (2019)
- Usual adult range
- 3 and above ng/mL
Vitamin D (25-Hydroxy)
BSG suggests measuring vitamin D in Crohn's disease and ulcerative colitis, and ACG lists vitamin D among the other tests that may be part of celiac follow-up.
Sources: British Society of Gastroenterology (2019) and American College of Gastroenterology (2023)
- Usual adult range
- 30–100 ng/mL
Albumin
In IBD, a very low albumin reflects significant inflammation or poor absorption, BSG notes. It often goes with poor nutrition but is not itself a measure of nutrition, and BSG says correcting it depends mainly on treating the inflammation.
- Usual adult range
- 3.5–5 g/dL
Alanine Aminotransferase (ALT)
Raised liver enzymes can be part of untreated celiac disease, often without symptoms, and ACG suggests that people with unexplained raised liver enzymes be checked for celiac disease. These gluten-related rises return to normal on a gluten-free diet in most people.
- Men, 18+
- 0–44 U/L
- Women, 18+
- 0–32 U/L
Ranges shown are the usual adult ranges labs print. The range on your own report is the one your result is judged against.
Getting results you can compare
- Celiac blood tests are meant to be done on a regular diet that includes gluten. For people already gluten-free, ACG notes that an HLA-DQ2/DQ8 test can come first, and a gluten challenge can be offered if it is positive.
- Once celiac disease is confirmed, ACG describes several visits in the first year (for example at 3, 6 and 12 months), then once or twice a year, with blood tests chosen to recheck whatever was abnormal at the start.
- For Crohn's disease in remission, AGA suggests checking CRP and calprotectin every 6 to 12 months, and every 2 to 4 months when symptoms increase.
- Gut infections raise calprotectin too, so a high result during a stomach bug can mislead. BSG notes it can't tell IBD from gastroenteritis on its own.
Good to know
- Inflammation raises ferritin, which can hide low iron. In IBD with active inflammation, BSG says a ferritin up to 100 µg/L (100 ng/mL) may still reflect iron deficiency.
- A negative tTG-IgA on a gluten-free diet is a good sign, but it doesn't prove the gut has healed. ACG notes that blood tests match gut healing poorly, and a repeat biopsy is the only reliable way to check it.
Questions you could ask
- Was my total IgA checked along with my celiac test?
- How often should we recheck my tTG-IgA and nutrient levels?
- Would checking calprotectin or CRP help track my IBD between scopes?
- Could inflammation be affecting my ferritin result?
- Which vitamins and minerals are worth checking for me?
Sources
- American College of Gastroenterology Guidelines Update: Diagnosis and Management of Celiac Disease, American College of Gastroenterology (2023)
- British Society of Gastroenterology consensus guidelines on the management of inflammatory bowel disease in adults, British Society of Gastroenterology (2019)
- The role of biomarkers for the management of Crohn's disease, American Gastroenterological Association (2023)
- First comprehensive guideline on using biomarkers for monitoring Crohn's disease, American Gastroenterological Association (2023)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-19. How we build and check these pages.
Educational information, not medical advice. Blood Test Tracker doesn’t diagnose or treat, and it doesn’t replace your clinician. Talk with your clinician before changing medications, supplements or care.