How doctors test for celiac disease
Testing for celiac disease happens in two stages. First, your doctor orders blood tests to look for specific antibodies your body makes when you eat gluten. If those tests are positive or inconclusive, the second stage is an endoscopy—a procedure where a thin camera goes down your throat to take small tissue samples from your small intestine. A pathologist then examines those samples under a microscope to confirm the diagnosis.
You must be eating gluten regularly when you have these tests done. If you stop eating gluten before testing, the antibodies disappear and the intestinal damage heals, which can make the tests come back negative even if you have celiac disease. This is why doctors ask you to keep gluten in your diet until testing is complete.
Key Takeaways
- Blood tests that look for tissue transglutaminase (tTG) antibodies are the first step and can be done at any lab your doctor orders.
- You must continue eating gluten-containing foods for at least several weeks before blood tests, or the results may be falsely negative.
- If blood tests suggest celiac disease, your doctor will refer you to a gastroenterologist for an endoscopy to confirm the diagnosis with intestinal biopsy samples.
- The endoscopy takes about 15 to 30 minutes and uses sedation, so you will need someone to drive you home afterward.
- From your first blood test to a confirmed diagnosis typically takes four to eight weeks, depending on how quickly your doctor schedules the endoscopy.
Blood tests: what your doctor is looking for
The main blood test is called tissue transglutaminase (tTG) serology. When you have celiac disease and eat gluten, your immune system attacks an enzyme in your intestines called tissue transglutaminase. Your body then makes antibodies against this enzyme. The blood test measures whether these antibodies are present and how much of them you have.
Your doctor may also order an endomysial antibody (EMA) test, which looks for a different antibody your body makes in response to gluten. Some doctors order both tests together because they confirm each other. If one is positive and the other is negative, it can mean the result is unclear and you may need more testing.
A third test, called total serum IgA, checks whether your body makes enough of a protein called IgA. Some people have an IgA deficiency, which can make the other antibody tests unreliable. If your IgA is low, your doctor may order different tests instead.
Preparing for blood tests
Before your blood test, continue eating gluten as you normally do. Gluten is found in wheat, barley, and rye. Common sources include bread, pasta, cereals, baked goods, and many processed foods. If you have already stopped eating gluten, talk to your doctor—you may need to eat gluten again for several weeks before testing to get accurate results.
Blood tests themselves require no special preparation. You can eat and drink normally on the day of the test. The lab will draw a small sample of blood from your arm, usually into one or two vials. Results typically come back within a few days to a week.
What happens if blood tests are positive
A positive blood test means antibodies were found, which suggests celiac disease. However, a positive blood test alone does not confirm the diagnosis. Your doctor will refer you to a gastroenterologist—a doctor who specializes in digestive system disorders—to perform an endoscopy and take tissue samples from your small intestine.
The gastroenterologist's office will contact you to schedule the procedure. This usually happens within two to four weeks, though it can be longer depending on how busy the office is. When you call to schedule, ask how long the wait is and whether there is a cancellation list if you need an earlier appointment.
The endoscopy procedure
An endoscopy is a procedure in which a thin, flexible tube with a camera on the end is passed down your throat, through your stomach, and into your small intestine. The doctor uses the camera to look at the lining of your intestine and takes several small tissue samples using tiny tools that fit through the tube. These samples are painless to take—you will not feel them being removed.
The procedure takes about 15 to 30 minutes. You will be given sedation (medication to make you drowsy or unconscious) through an IV, so you will not remember the procedure. Your throat may be numbed with a spray first. You must have someone drive you home because the sedation affects your ability to drive safely for the rest of the day.
Before the endoscopy, you will need to fast—not eat or drink anything—for six to eight hours. Your doctor's office will give you exact instructions about when to stop eating and drinking. If you take regular medications, ask whether you should take them on the morning of the procedure.
After the endoscopy and biopsy results
After the endoscopy, you may have a sore throat for a day or two, and you might feel bloated or have mild cramping as the air used during the procedure leaves your system. These symptoms are normal and usually go away within 24 hours. You can eat and drink normally once you are fully awake, though your doctor may recommend starting with bland foods.
The tissue samples are sent to a pathologist, who examines them under a microscope to look for damage to the intestinal lining. In celiac disease, the villi (finger-like projections that line the small intestine) become flattened and damaged. The pathologist grades the damage on a scale and writes a report that goes to your gastroenterologist.
Your gastroenterologist will review the pathology report and contact you with the results, usually within one to two weeks. If the biopsy shows the characteristic damage of celiac disease, you will be diagnosed with celiac disease. If the biopsy is normal but your blood tests were positive, your doctor may discuss other reasons for the antibodies or recommend repeat testing in the future.
Testing if you have symptoms of non-celiac gluten sensitivity
Some people have symptoms similar to celiac disease—bloating, diarrhea, fatigue, headaches—but their blood tests and biopsies are both normal. This may indicate non-celiac gluten sensitivity, a different condition. There is no blood test or biopsy for non-celiac gluten sensitivity. Instead, doctors diagnose it by ruling out celiac disease and wheat allergy first, then observing whether symptoms improve when gluten is removed from the diet.
If your celiac disease tests are negative but you still suspect gluten is causing your symptoms, talk to your doctor about a trial elimination diet—removing gluten for several weeks to see if symptoms improve. Keep a food and symptom diary during this time to help your doctor understand the pattern.
Frequently Asked Questions
Can I get tested for celiac disease without eating gluten?
Testing is much less reliable if you are not eating gluten. The antibodies your body makes in response to gluten disappear within weeks of stopping gluten, and the intestinal damage begins to heal. If you have already stopped eating gluten, ask your doctor whether you should resume it for several weeks before testing, or whether genetic testing might be an option in your situation.
How much does celiac disease testing cost?
The cost varies depending on your insurance coverage and whether you have met your deductible. Blood tests typically cost between $100 and $300 out of pocket if uninsured, and endoscopy with biopsy can range from $1,000 to $3,000. Contact your doctor's office and the gastroenterology clinic to ask about their cash prices, and check with your insurance company about what they cover.
What if my blood test is negative but I still have symptoms?
A negative blood test makes celiac disease unlikely, but it is not impossible. If you were not eating enough gluten at the time of testing, or if you have IgA deficiency, results can be falsely negative. Talk to your doctor about whether repeat testing makes sense, or whether other conditions might explain your symptoms.
Can children be tested for celiac disease?
Yes. Children can have blood tests and endoscopy just as adults do. The same rule applies—they must be eating gluten when tested. Some pediatricians refer children directly to a pediatric gastroenterologist, while others do the blood test first and refer only if it is positive.
How long does it take to get a diagnosis?
From your first blood test to a confirmed diagnosis usually takes four to eight weeks. This includes time for the blood test results to come back, scheduling the endoscopy, performing the procedure, and waiting for the pathology report. If there are delays in scheduling or if additional testing is needed, it can take longer.