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Celiac Disease Diagnosis: Complete Testing Guide (2026)

Think you might have celiac disease? Here's exactly how to get tested — which blood tests to ask for, what to expect from an endoscopy, and common mistakes.

By Check Gluten Team · February 22, 2026


Getting the Right Diagnosis


If you suspect celiac disease, getting properly tested is crucial. Many people make the mistake of going gluten-free before testing — which makes diagnosis nearly impossible.


Step 1: Blood Test


The Primary Test: tTG-IgA (Tissue Transglutaminase)

This is the gold standard screening test for celiac disease. It measures your body's immune response to gluten.


  • •Accuracy: — 93% sensitivity, 97% specificity
  • •Cost: — Usually $50-150 (often covered by insurance with symptoms)
  • •How it works: — A simple blood draw at your doctor's office or lab

    • Additional Blood Tests Your Doctor May Order

  • •Total IgA — rules out IgA deficiency (which causes false negatives on tTG)
  • •DGP-IgG — (Deamidated Gliadin Peptide) — useful if you're IgA-deficient
  • •EMA (Endomysial Antibody) — very specific but expensive

    • ⚠️ CRITICAL: You Must Be Eating Gluten

    For accurate results, you need to be eating the equivalent of at least 2 slices of bread per day for 6-8 weeks before your blood test.


    If you've already gone GF, your antibodies may have dropped — leading to a false negative.


    Step 2: Endoscopy with Biopsy


    If your blood tests are positive, the next step is an upper endoscopy (EGD):


    What to Expect

  • The procedure takes 15-20 minutes
  • You're sedated — most people don't remember it
  • A thin scope goes through your mouth to your small intestine
  • The doctor takes 4-6 tiny biopsies from the duodenum
  • Biopsy samples are examined for villous atrophy (flattened intestinal villi)

    • Is It Painful?

    No — you're sedated. Most people say the worst part is not eating before the procedure (you fast for 8-12 hours).


    Marsh Scale (Biopsy Grading)

    GradeDescriptionDiagnosis
    Marsh 0NormalNo celiac
    Marsh 1Increased lymphocytesPossible early celiac
    Marsh 2Lymphocytes + crypt hyperplasiaProbable celiac
    Marsh 3aPartial villous atrophyConfirmed celiac
    Marsh 3bSubtotal villous atrophyConfirmed celiac
    Marsh 3cTotal villous atrophyConfirmed celiac (severe)

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    Step 3: Genetic Testing (Optional)


    HLA-DQ2 and HLA-DQ8

    These genetic markers are found in virtually all celiac patients:

  • •HLA-DQ2: — Present in ~95% of celiacs
  • •HLA-DQ8: — Present in most of the remaining ~5%

    • When Genetic Testing Helps

  • •Ruling OUT celiac: — If you don't have DQ2 or DQ8, you almost certainly don't have celiac
  • •Family screening: — If a family member has celiac, genetic testing tells you if you're at risk
  • •Already gluten-free: — If you went GF before blood testing, genetic testing still works

    • Common Diagnosis Mistakes


    1. Going GF Before Testing

    The #1 mistake. Your antibodies drop within weeks of going GF, leading to false negative blood tests and biopsies.


    2. Not Taking Enough Biopsies

    Celiac damage can be patchy — one area may be damaged while the area next to it looks normal. The doctor should take at least 4 biopsies from different areas.


    3. Only Getting Blood Tests

    Blood tests screen for celiac but don't confirm it. An endoscopy with biopsy is needed for definitive diagnosis.


    4. Accepting an IBS Diagnosis Without Celiac Testing

    Studies show up to 1 in 10 people diagnosed with IBS actually have celiac disease. Always request celiac testing before accepting an IBS diagnosis.


    5. Not Testing Family Members

    If you're diagnosed, all first-degree relatives should be tested. Celiac has a 10% hereditary rate in first-degree relatives.


    What Happens After Diagnosis


  • Start a strict gluten-free diet — immediately
  • See a GF-specialized dietitian — they'll teach you what to eat and avoid
  • Get baseline blood work — check for deficiencies (iron, vitamin D, B12, calcium, folate)
  • Bone density scan — celiac increases osteoporosis risk
  • Download Check Gluten — your daily tool for verifying safe foods
  • Schedule follow-up blood tests — every 3-6 months initially, then annually
  • Join a support group — you're not alone

    • The Bottom Line


    Getting diagnosed correctly requires the right tests in the right order — while still eating gluten. Don't skip steps. A proper diagnosis ensures you get appropriate medical follow-up, insurance coverage, and the motivation to stay strictly GF for life.


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