“How Celiac Disease Is Diagnosed: Blood Tests, Biopsy, and Why You Keep Eating Gluten
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Published October 10, 2026 Staci Leibson – Life Coach at The Celiac Shift |
How Is Celiac Disease Diagnosed?
Celiac disease is usually diagnosed in two steps: a blood test that looks for antibodies your body makes in reaction to gluten, followed in most cases by a small intestine biopsy taken during an endoscopy. Keep eating gluten until all testing is finished, because going gluten-free first can make results look falsely normal.
How Is Celiac Disease Diagnosed?
Celiac disease is usually diagnosed in two steps: a blood test that looks for antibodies your body makes in reaction to gluten, followed in most cases by a small intestine biopsy taken during an endoscopy. Keep eating gluten until all testing is finished, because going gluten-free first can make results look falsely normal.
If you have noticed possible signs of celiac disease in yourself or your child, our guide to celiac disease symptoms and early warning signs explains what to look for. This page picks up from there and walks through what testing actually involves, step by step.
Why You Need to Keep Eating Gluten Before Testing
Celiac tests do not look for gluten itself. They look for your body’s reaction to gluten: the antibodies your immune system makes and the damage it does to the lining of your small intestine. When you stop eating gluten, those antibodies start to fade, and the intestine begins to heal. That is good for your health, but it can make a test come back normal even when you do have celiac disease.
That is why the National Institutes of Health advises against starting a gluten-free diet before testing. Keep eating your usual foods with gluten until your doctor says all testing, including any biopsy, is complete.
Already cut back on gluten? Tell your doctor before you add it back. Do not restart gluten on your own to “get ready” for a test. Your doctor can decide whether you need a supervised gluten challenge, explained further down this page.
Step 1: The Celiac Blood Test
For most children and adults, testing starts with a simple blood draw. The main test is called tTG-IgA (tissue transglutaminase IgA). It measures an antibody that is usually high in people with celiac disease who are eating gluten.
According to the Celiac Disease Foundation, the tTG-IgA test is positive in about 93 percent of people with celiac disease who eat gluten, and negative in about 96 percent of people who do not have it. That makes it a strong first step, but not a final answer.
Why doctors also check your total IgA
Some people naturally make very little IgA, the type of antibody the main test measures. This is called IgA deficiency, and it is more common in people with celiac disease. If your IgA is low, the tTG-IgA test can come back falsely normal. So doctors usually order a total IgA test at the same time. If it is low, they switch to tests that measure a different antibody type, IgG.
The celiac blood tests at a glance
| Test | What it checks | When it is used |
| tTG-IgA | The main celiac antibody | First test for most children and adults |
| Total IgA | Whether your body makes enough IgA for the main test to work | Usually ordered alongside tTG-IgA |
| EMA-IgA (endomysial antibody) | A second celiac antibody that is very rarely positive without celiac disease | To double-check results or in hard-to-read cases |
| DGP (deamidated gliadin peptide) IgA and IgG | Antibodies to broken-down gluten proteins | For people with low IgA, and often added for children about age 2 and younger |
| tTG-IgG | The main antibody, measured as IgG instead of IgA | For people with low IgA |
A positive blood test strongly suggests celiac disease but does not confirm it on its own. False positives can happen, especially in people with other autoimmune conditions such as type 1 diabetes or thyroid disease. That is why the next step is usually a look at the intestine itself.
Step 2: The Small Intestine Biopsy
If your blood test is positive, or your doctor strongly suspects celiac disease even with a normal blood test, you will usually be referred to a gastroenterologist, a doctor who specializes in the digestive system. The American College of Gastroenterology recommends confirming the diagnosis with an upper endoscopy and several small biopsies in both children and adults.
What happens during an endoscopy
- You are usually given medicine to help you relax or sleep. It is typically an outpatient procedure, meaning you go home the same day.
- The doctor guides a thin, flexible tube with a tiny camera through your mouth, past your stomach, and into the first part of the small intestine.
- Using a small tool passed through the tube, the doctor takes several tiny tissue samples from different spots.
- A specialist called a pathologist looks at the samples under a microscope for signs of celiac damage, especially flattened villi. Villi are tiny, finger-like bumps that line the intestine and absorb nutrients from food.
You still need to be eating gluten on the day of your endoscopy. Stopping between the blood test and the biopsy can make the biopsy look normal.
A note about the skin rash
If you have the itchy, blistering rash linked to celiac disease, called dermatitis herpetiformis, a doctor may confirm the diagnosis with a small skin biopsy instead.
Can Celiac Disease Be Diagnosed Without a Biopsy?
Sometimes, in children. When a child’s tTG-IgA level is very high, at least 10 times the lab’s normal limit, and a second, separate blood sample is positive for EMA, some pediatric gastroenterologists may confirm celiac disease without an endoscopy. This approach comes from European pediatric guidelines, and the authors of the 2023 American College of Gastroenterology guideline support it for children with very high levels.
For adults in the United States, a biopsy is still the standard way to confirm the diagnosis. Some newer European guidelines allow blood tests alone for certain adults, so ask your gastroenterologist which approach fits your situation.
What Genetic Testing Can and Cannot Tell You
Almost everyone with celiac disease carries one or both of two gene types called HLA-DQ2 and HLA-DQ8. A genetic test can check for them using a blood sample or a cheek swab.
- If you do not carry either gene, you are very unlikely to have or ever develop celiac disease. This can save you from future testing.
- If you do carry one, it does not mean you have celiac disease. The Celiac Disease Foundation notes that up to 25 to 30 percent of people carry these genes, and most never develop celiac disease.
Unlike the blood test and biopsy, a genetic test works whether or not you are eating gluten, and it can be done at any age. That makes it especially useful for people who have already gone gluten-free, for unclear test results, and for family members. Genetic testing can cost several hundred dollars, so check with your insurance plan first.
Already Gluten-Free? What a Gluten Challenge Involves
If you stopped eating gluten before being tested, your doctor may suggest a gluten challenge. This means eating a set amount of gluten every day for several weeks so your body has time to react, and then being tested.
The exact plan varies. Celiac Canada describes two common approaches for adults:
| Approach | Daily amount | How long |
| Standard challenge | 6 to 10 grams of gluten, about 2 to 3 slices of wheat bread | 6 to 8 weeks |
| Lower-dose challenge | 3 grams of gluten, about 1.5 slices of wheat bread | At least 6 weeks |
Your doctor may repeat the blood test partway through. A few important cautions:
- Only do a gluten challenge with a doctor’s guidance, ideally one experienced with celiac disease. Your doctor sets the amount and length for you.
- The Celiac Disease Foundation advises never doing a gluten challenge while pregnant.
- If your symptoms become severe, contact your doctor right away. They may move you to a biopsy sooner.
- Many doctors order a genetic test first. If you do not carry either celiac gene, you may be able to skip the challenge entirely.
Testing Family Members
Celiac disease runs in families. The Celiac Disease Foundation reports that parents, brothers and sisters, and children of someone with celiac disease have about a 1 in 10 chance of having it, compared with about 1 in 100 in the general population. Family members can have celiac disease without any obvious symptoms.
If someone in your family has been diagnosed, ask your own doctor about a celiac blood test. A genetic test can also help: family members who do not carry either gene can usually stop worrying, while those who do may be advised to repeat blood testing every few years or right away if symptoms appear.
What a Negative Result Does and Does Not Mean
A normal blood test usually means celiac disease is unlikely, but not always. Results can be falsely normal if you were not eating enough gluten, if your total IgA is low and was not checked, or, rarely, if you have celiac disease that does not show up in blood tests. If your results are normal but your symptoms continue, go back to your doctor and ask about next steps. Do not go gluten-free on your own to “see if it helps” until that conversation has happened.
If you try an at-home celiac test kit, share the result with your doctor. A home kit does not replace a doctor-ordered blood test and, for most people, a biopsy.
Questions to Ask Your Doctor About Celiac Testing
Bringing a short list to your appointment can make the visit less overwhelming. Here are questions many families find helpful:
- Which celiac blood tests are you ordering, and is total IgA included?
- Should I keep eating gluten until every test is done, and roughly how much?
- I have already cut back on gluten. Do I need a gluten challenge or a genetic test first?
- If my blood test is positive, will I need an endoscopy, and who will do it?
- Should my parents, siblings, or children be tested too?
- If I am diagnosed, who will help me with follow-up care and the gluten-free diet?
What Happens After a Diagnosis
Once celiac disease is confirmed, the treatment is a strict, lifelong gluten-free diet. Your gastroenterologist will monitor your healing, often with follow-up blood tests, and may check for low nutrient levels. A registered dietitian can help with the nutrition side.
The part many families find hardest is turning “go gluten-free” into daily life at home, at school, and when eating out. That is where celiac coaching helps. Coaching is non-medical and works alongside your doctor and dietitian, not in place of them. Learn more about [how celiac coaching works] or [book a free consultation] with Staci Leibson.
Frequently Asked Questions
Can I be tested for celiac disease if I already eat gluten-free?
Blood tests and biopsies are not reliable once you have stopped eating gluten. A genetic test still works and can show whether celiac disease is possible. If it is, your doctor may recommend a supervised gluten challenge before testing.
Can I test positive and not have celiac disease?
Yes. Blood tests can occasionally be positive in people without celiac disease, especially those with other autoimmune conditions. That is why most people are asked to have a biopsy to confirm the result.
Is a genetic test enough to diagnose celiac disease?
No. Carrying HLA-DQ2 or HLA-DQ8 only means celiac disease is possible. A negative genetic test is more useful, because it makes celiac disease very unlikely.
Does an endoscopy hurt?
Most people are given medicine to relax or sleep during the procedure and do not remember it. A mild sore throat afterward is common. Ask your doctor what to expect for you or your child.
Do I need to keep eating gluten between the blood test and the biopsy?
Yes. Keep eating gluten until your doctor confirms that all testing, including the biopsy, is complete.
Please refer to our Complete Guide to Celiac Disease for additional information about gluten and Celiac Disease.
This page is general education written by a non-medical celiac coach and built from the public health and clinical guideline sources listed below. It cannot diagnose celiac disease or replace care from a doctor.