How celiac testing works

Celiac testing happens in two stages: a blood test first, then an endoscopy with a biopsy if the blood test is positive. Your doctor orders the blood test, which looks for specific antibodies your body makes when you eat gluten. If those antibodies are present, the endoscopy confirms the diagnosis by showing damage to your small intestine.

The entire process usually takes several weeks from first appointment to final results. You do not need a referral to see your primary care doctor about celiac symptoms, but you will need a referral to a gastroenterologist for the endoscopy.

Key Takeaways

  • Blood tests for celiac look for tissue transglutaminase (tTG) antibodies and must be done while you are still eating gluten regularly.
  • An endoscopy with biopsy is the only way to confirm celiac disease; a positive blood test alone is not a diagnosis.
  • You should continue eating gluten until testing is complete, because a gluten-free diet will make antibodies disappear and give a false negative result.
  • Most insurance covers celiac testing when ordered by your doctor, though you may have a copay or deductible.

The blood test: what to expect

Your doctor will order a blood test that measures tissue transglutaminase (tTG) antibodies, usually the tTG-IgA test. This is a standard lab test done at a hospital lab, clinic lab, or sometimes a walk-in lab. You sit in a chair, a technician draws blood from your arm, and the sample goes to a lab for analysis. Results typically come back within a few days to a week.

The blood test is not painful beyond the needle stick, and you do not need to fast or prepare in any special way. However, you must be eating gluten regularly at the time of the test. If you have already stopped eating gluten, the antibodies will have started to disappear, and the test may show negative even if you have celiac disease. This is why it is important to keep eating gluten until your doctor tells you testing is complete.

A positive tTG-IgA test means your body is making antibodies in response to gluten, which is a strong sign of celiac disease. However, a positive blood test is not a diagnosis by itself. Some people have positive antibodies but no intestinal damage. Your doctor will discuss the results with you and explain the next step.

The endoscopy and biopsy: what to expect

If your blood test is positive, your doctor will refer you to a gastroenterologist, a specialist in digestive health. The gastroenterologist performs an upper endoscopy, a procedure where a thin tube with a camera is passed down your throat into your small intestine. During the procedure, the doctor takes small tissue samples (a biopsy) from the lining of your small intestine.

The endoscopy is done under sedation, so you will not feel pain or remember the procedure. You will need someone to drive you home afterward because the sedation takes several hours to wear off. The procedure itself takes about 15 to 30 minutes. You cannot eat or drink for 6 to 8 hours before the procedure, and your doctor will give you specific instructions about what to stop eating the night before.

The tissue samples are examined under a microscope to look for damage to the intestinal lining, which is called villous atrophy. This damage is the hallmark of celiac disease. If the biopsy shows this damage, you have celiac disease. If the biopsy is normal, celiac disease is ruled out, even if your blood test was positive.

Timing and what to do while waiting

From your first appointment with your primary care doctor to your final diagnosis usually takes 4 to 8 weeks, depending on how quickly you can get appointments and how fast the labs process samples. The blood test results come back in days, but getting a gastroenterology appointment can take weeks in some areas.

While you are waiting for testing, keep eating gluten as you normally do. Do not start a gluten-free diet, because it will interfere with the blood test and biopsy results. If you have already cut back on gluten, tell your doctor before the blood test, because they may need to adjust how they interpret the results.

If you have severe symptoms like chronic diarrhea or malnutrition, your doctor may prioritize getting you to a gastroenterologist faster. In some cases, doctors will refer you directly to gastroenterology without waiting for blood test results if symptoms are very severe.

Insurance and cost

Most insurance plans cover celiac blood testing and endoscopy when ordered by your doctor. You will likely have a copay for the office visit and possibly a separate copay for the lab work. If you have not met your deductible, you may owe the full cost of the lab test until you do.

The endoscopy is more expensive than the blood test, often costing several hundred dollars even with insurance, though your insurance will cover most of it. Ask your gastroenterologist's office what your out-of-pocket cost will be before the procedure. If you do not have insurance, some hospitals and clinics offer reduced-cost testing based on income.

What happens after diagnosis

If the biopsy confirms celiac disease, your doctor will refer you to a dietitian who specializes in celiac disease. The dietitian teaches you how to read food labels, avoid hidden sources of gluten, and plan meals that are safe. You will also learn about cross-contamination in your kitchen and how to prevent it.

Once you start a gluten-free diet, your intestines begin to heal. Most people feel better within days or weeks, though complete healing of the intestinal lining can take months or years. Your doctor will monitor your health with follow-up blood tests and may repeat the endoscopy after a year or two to confirm that your intestines have healed.

Frequently Asked Questions

Can I get tested if I am already on a gluten-free diet?

Testing will not be accurate if you are already gluten-free. You need to eat gluten regularly for at least 2 to 4 weeks before the blood test so that antibodies can build up. If you have been gluten-free for longer, talk to your doctor about whether to reintroduce gluten before testing or whether other testing options exist.

What if my blood test is negative but I still have symptoms?

A negative blood test means celiac disease is unlikely, but it does not rule out other conditions that cause similar symptoms, such as non-celiac gluten sensitivity or irritable bowel syndrome. Your doctor can order other tests or refer you to a gastroenterologist to look for other causes.

Do I need to see a specialist to get tested, or can my regular doctor do it?

Your primary care doctor can order the blood test and discuss the results with you. However, you will need a referral to a gastroenterologist to have the endoscopy and biopsy done. Some insurance plans require a referral; others do not. Check your insurance card or call your insurance company to find out.

How long does it take to get results from the biopsy?

Biopsy results usually come back within 1 to 2 weeks. Your gastroenterologist will call you or schedule a follow-up appointment to discuss the results and explain what they mean for your health.

Will the endoscopy show other problems besides celiac disease?

Yes. During the endoscopy, the gastroenterologist can see the entire upper part of your digestive tract and may spot other issues like ulcers, inflammation, or polyps. If something else is found, your doctor will discuss treatment options with you.