Celiac disease screening: who is tested, the blood test and what comes next
Celiac disease is an autoimmune condition triggered by gluten, a protein in wheat, rye and barley. In people with the condition, eating gluten causes inflammation that damages the small intestine. (USPSTF, 2017) It is usually found with an antibody blood test, and in most people a biopsy of the small intestine confirms it. (ACG, 2023) (NIDDK)
Screening people without symptoms
The USPSTF found the evidence insufficient to weigh the benefits and harms of screening adults, teens and children who have no symptoms, so it makes no recommendation (an I statement, 2017). A literature scan in May 2024 found no new evidence to justify an update. The USPSTF also found too little evidence on targeted screening of people at higher risk. (USPSTF, 2017) NIDDK says doctors in the United States do not routinely screen people for celiac disease. (NIDDK)
The USPSTF lists possible harms of screening people without symptoms: false-positive or unclear blood results, biopsies that turn out not to be needed, and worry. It estimates that at a prevalence of about 1%, only 12% to 40% of positive blood tests would be true positives; in higher-risk groups, 40% to 80%. Some people diagnosed this way may never develop symptoms, so overdiagnosis is also a concern. (USPSTF, 2017) For other tests with an unclear balance, see screening tests you may not need.
Who is tested
Celiac disease is not diagnosed from symptoms alone, because some symptoms look like those of other digestive conditions. (NIDDK) NICE advises offering the blood test to:
- People with symptoms or signs: persistent unexplained stomach or bowel symptoms, faltering growth, prolonged tiredness, unexpected weight loss, severe or persistent mouth ulcers, unexplained low iron, vitamin B12 or folate, and irritable bowel syndrome in adults. (NICE NG20, 2015)
- People with type 1 diabetes or autoimmune thyroid disease: at the time of diagnosis. (NICE NG20, 2015)
- First-degree relatives (parent, sibling or child) of people with celiac disease. (NICE NG20, 2015) (NHS) The USPSTF cites an estimated 5% to 20% prevalence in people with a family history. (USPSTF, 2017)
NICE says to consider testing people with reduced bone density or osteomalacia, unexplained nerve symptoms (particularly peripheral neuropathy or ataxia), unexplained subfertility or repeated miscarriage, persistently raised liver enzymes with no known cause, dental enamel defects, Down syndrome or Turner syndrome. (NICE NG20, 2015) The USPSTF also lists IgA deficiency and IgA nephropathy among the conditions linked with higher risk. (USPSTF, 2017) See screenings if you have diabetes, iron test results, vitamin B12 test results and bone density test results.
The blood tests
The test is a blood sample from a vein in your arm and usually takes less than five minutes. (MedlinePlus, celiac screening)
| Test | What it looks for |
|---|---|
| Tissue transglutaminase IgA (tTG-IgA) | Antibodies that are often higher than normal in people with untreated celiac disease. It is the most commonly used test and the usual first choice. (NIDDK) (MedlinePlus, celiac screening) (NICE NG20, 2015) (USPSTF, 2017) |
| Total IgA | Whether you have a deficiency of IgA, which can happen in people with celiac disease. NICE asks labs to test total IgA together with tTG-IgA, and to use IgG tests if IgA is deficient. (MedlinePlus, celiac screening) (NICE NG20, 2015) |
| IgA endomysial antibodies (EMA) | A second antibody test. NICE uses it when tTG-IgA is only weakly positive. (NICE NG20, 2015) |
| IgG tests (DGP, EMA or tTG) | Antibody tests used when IgA is low. MedlinePlus says the DGP test is also used in children younger than 2. (NICE NG20, 2015) (MedlinePlus, celiac screening) |
| Genetic test (HLA DQ2 and DQ8) | Gene variants linked to celiac disease. Without them, celiac disease is very unlikely; having them does not mean you have it. NICE keeps this test for specialist settings. (NIDDK) (NICE NG20, 2015) |
The USPSTF found that the tTG-IgA test has high (more than 90%) sensitivity and specificity in studies that included people with symptoms, but the few studies of people without symptoms found lower accuracy. (USPSTF, 2017)
Why gluten stays in the diet before testing
The tests look for the body's reaction to gluten, so they are accurate only if you are eating gluten while you are tested. NICE suggests eating some gluten in more than 1 meal every day for at least 6 weeks before testing. (NICE NG20, 2015) MedlinePlus says to keep eating foods with gluten for a few weeks before the test, and that your provider will give you specific instructions. (MedlinePlus, celiac screening) NIDDK says doctors do not recommend starting a gluten-free diet before testing because it can affect the results. (NIDDK)
- If you have already cut down or stopped gluten and cannot start eating it again, NICE says to refer you to a specialist and to explain that it may be difficult to confirm the diagnosis by biopsy. (NICE NG20, 2015)
- NICE says not to test babies before gluten has been introduced into their diet. (NICE NG20, 2015)
What the results mean
- Negative: you probably do not have celiac disease. (MedlinePlus, celiac screening) It is sometimes possible to have it without the antibodies, so if symptoms continue you may still be referred to a specialist. (NHS) (NICE NG20, 2015) NICE says people who test negative, especially first-degree relatives and people with type 1 diabetes, should see a health professional if symptoms appear or continue, and asks doctors to have a low threshold for testing again if symptoms develop. (NICE NG20, 2015)
- Positive: you probably have celiac disease, and more tests are used to confirm it. (MedlinePlus, celiac screening) For adults, NICE defines a positive result as a clearly positive tTG-IgA, or a weakly positive tTG-IgA with a positive EMA. (NICE NG20, 2015)
- Uncertain or indeterminate: it is unclear whether you have celiac disease, and your provider may order more tests. (MedlinePlus, celiac screening)
What a positive result leads to
NICE refers adults with a positive blood test to a specialist in stomach and bowel conditions for a biopsy of the small intestine, to confirm or rule out celiac disease. Children are referred to a children's specialist, and further tests may include an EMA blood test, a genetic test or a biopsy. (NICE NG20, 2015) The biopsy is taken during an upper endoscopy: a thin flexible tube with a camera is passed through the mouth to the first part of the small intestine, small pieces of tissue are taken, and a pathologist looks at them under a microscope. (NIDDK) (NHS) If you have a rash that could be linked to celiac disease, a skin biopsy may be done. (NIDDK)
NICE and the NHS both say not to start a gluten-free diet until a specialist confirms the diagnosis, even if the blood test is positive. (NICE NG20, 2015) (NHS)
Where they differ:
- Testing people without symptoms: the USPSTF makes no recommendation for or against screening people without symptoms, including higher-risk groups, (USPSTF, 2017) while NICE offers the blood test to first-degree relatives and to people with type 1 diabetes or autoimmune thyroid disease at diagnosis. (NICE NG20, 2015) NIDDK suggests relatives and people with type 1 diabetes talk with their doctor about testing. (NIDDK)
- Biopsy in children: NICE lists a biopsy among the possible next steps for children with a positive result, (NICE NG20, 2015) while the ACG 2023 update says a biopsy is needed in most patients and suggests a nonbiopsy route for diagnosis in selected children. (ACG, 2023)
- How long to eat gluten first: NICE gives at least 6 weeks, (NICE NG20, 2015) while MedlinePlus says a few weeks and leaves the details to your provider. (MedlinePlus, celiac screening)
Your doctor decides what your result means for you.
This page does not give diet or treatment advice. If you have a flagged result, see after an abnormal screening result for questions to ask.
Questions people ask
Should I be screened for celiac disease if I have no symptoms?
The USPSTF found too little evidence to recommend for or against screening people without symptoms (an I statement, 2017). A 2024 literature scan found no new evidence to update it. NIDDK says US doctors do not routinely screen, but blood relatives of people with celiac disease and people with type 1 diabetes should talk with their doctor about whether to be tested. (USPSTF, 2017) (NIDDK)
Do I need to eat gluten before a celiac blood test?
Yes, if the test is to diagnose celiac disease. NICE says the tests are accurate only if you eat gluten during the diagnostic process, and suggests eating some gluten in more than 1 meal every day for at least 6 weeks before testing. MedlinePlus says to keep eating foods with gluten for a few weeks before testing. Your provider gives you the instructions. (NICE NG20, 2015) (MedlinePlus, celiac screening)
Does a positive blood test mean I have celiac disease?
Not on its own. MedlinePlus says a positive result means you probably have it, and other tests may follow to confirm it. NICE refers adults with a positive result to a specialist for a biopsy of the small intestine to confirm or rule it out. Both NICE and the NHS say not to start a gluten-free diet until a specialist confirms the diagnosis. (MedlinePlus, celiac screening) (NICE NG20, 2015) (NHS)
Can the blood test be negative when I do have celiac disease?
It can. The NHS says it is sometimes possible to have celiac disease without the antibodies in your blood, and a GP may still refer you to a specialist if symptoms continue. NICE says to refer people with a negative result if celiac disease is still suspected. (NHS) (NICE NG20, 2015)
Is the celiac blood test the same as the genetic test?
No. The blood test looks for antibodies. The genetic test looks for the DQ2 and DQ8 gene variants. NIDDK says that without these variants celiac disease is very unlikely, but most people who have them do not develop it, and your doctor may recommend more tests. (NIDDK)