Celiac disease is an autoimmune condition where eating gluten triggers your immune system to attack the lining of your small intestine. It affects roughly 1% to 2% of the population in countries where wheat is a dietary staple, though many cases go undiagnosed for years because the symptoms can look like dozens of other conditions. The damage it causes is real and cumulative, but it’s also one of the few autoimmune diseases with a clear, manageable trigger: gluten, a protein found in wheat, barley, and rye.
How Gluten Damages the Small Intestine
When you eat bread, pasta, or anything containing wheat, barley, or rye, your digestive system breaks gluten down into smaller protein fragments. In most people, these fragments pass through without issue. In someone with celiac disease, they resist complete digestion and slip through the intestinal lining into the tissue beneath it. There, an enzyme modifies these fragments in a way that makes the immune system treat them as a threat.
What follows is a three-pronged attack. Immune cells release inflammatory signals that destroy the tiny, finger-like projections (called villi) lining the small intestine. These villi are responsible for absorbing nutrients from food, so their destruction leads directly to malabsorption. At the same time, other immune cells produce antibodies against the body’s own tissue, and a third set of cells directly attacks the intestinal lining. Gluten also increases intestinal permeability, allowing even more of these protein fragments to cross the barrier and ramp up the immune response. It’s a self-reinforcing cycle that continues as long as gluten is in the diet.
Symptoms Go Far Beyond Digestion
The classic picture of celiac disease, with chronic diarrhea, bloating, weight loss, and poor nutrient absorption, is actually more common in children than adults. Kids may also show failure to thrive, short stature, and delayed puberty. Adults tend to present differently, often with symptoms that resemble irritable bowel syndrome: nausea, gas, and inconsistent bowel habits. About 20% of people with celiac disease have constipation as their main gut symptom, and roughly 40% are actually overweight or obese at the time of diagnosis, which can throw both patients and doctors off the trail.
The non-digestive symptoms are what make celiac disease so tricky to identify. Iron deficiency anemia shows up in about 40% of newly diagnosed cases, caused by the intestine’s inability to properly absorb iron. Bone thinning (osteoporosis) is common due to poor calcium and vitamin D absorption. Neurological symptoms range from chronic headaches and tingling in the hands and feet to anxiety and depression. Some people develop a specific itchy, blistering skin rash called dermatitis herpetiformis, which is so closely linked to celiac disease that it’s sometimes called “celiac of the skin.”
Celiac disease can also affect fertility. Both men and women may experience unexplained infertility, and women may have recurrent miscarriages, early menopause, or late onset of periods. Abnormal liver tests, mouth ulcers, and dental enamel defects round out the list of presentations that might never make someone think of a gut problem.
Getting an Accurate Diagnosis
The first step is a blood test, and the preferred one measures an antibody called tTG-IgA. This test has a sensitivity between 78% and 100% and a specificity between 90% and 100%, making it a strong screening tool. If the result is positive, a second confirmatory blood test (called EMA-IgA) can push diagnostic certainty even higher, with specificity reaching 97% to 100%. For young children under age 2, additional antibody tests may be combined because the standard test is less reliable at that age.
A small percentage of people have a condition called IgA deficiency, which can cause a false negative on the standard test. In those cases, alternative antibody tests that measure IgG instead of IgA are used.
For most adults, the diagnosis is confirmed with an intestinal biopsy, where a gastroenterologist takes tiny tissue samples from the small intestine during an upper endoscopy. The samples show the characteristic flattening of the villi. One critical detail: you need to be eating gluten regularly before testing. If you’ve already gone gluten-free, both blood tests and biopsies can come back falsely normal.
When a Biopsy Isn’t Needed
European guidelines now allow children to be diagnosed without a biopsy under specific conditions. If the initial antibody level is at least 10 times the upper limit of normal, and a second, separate blood sample confirms positive results on the EMA-IgA test, the diagnosis is considered secure. This no-biopsy approach applies even to children without symptoms, such as those screened because a sibling has celiac disease.
The Role of Genetics
Celiac disease has a strong genetic component. Nearly all people with the condition carry one of two gene variants: about 90% carry HLA-DQ2, around 5% carry HLA-DQ8, and the remaining 5% carry at least one copy of either gene. People who are homozygous for DQ2 (carrying two copies) face the highest risk.
Genetic testing won’t confirm celiac disease on its own, since roughly 30% to 40% of the general population carries these genes without ever developing the condition. But a negative genetic test is extremely useful for ruling it out. If you don’t carry HLA-DQ2 or HLA-DQ8, you can essentially cross celiac disease off the list. This is particularly helpful for people who’ve already started a gluten-free diet before being tested, since their antibody and biopsy results may be unreliable.
What Happens Without Treatment
Because celiac disease progressively damages the intestine’s ability to absorb nutrients, leaving it untreated creates a cascade of long-term problems. Calcium and vitamin D malabsorption leads to weakened bones. Iron and folate deficiency cause persistent anemia and fatigue. Poorly controlled celiac disease during pregnancy raises the risk of having a low-birth-weight baby.
There is also a small but real increased risk of certain cancers, including small bowel cancer, small bowel lymphoma, and Hodgkin lymphoma. Most people with celiac disease will never develop these, but the risk reinforces why diagnosis and dietary management matter even when symptoms seem mild or manageable.
Living on a Gluten-Free Diet
The only effective treatment for celiac disease is a strict, lifelong gluten-free diet. This means eliminating all foods containing wheat, barley, and rye. For most people, the intestinal lining begins to heal within weeks to months of removing gluten, and symptoms often improve even sooner. Complete villous recovery can take a year or longer in adults.
In the United States, the FDA requires any product labeled “gluten-free” to contain less than 20 parts per million of gluten. That translates to less than 20 milligrams of gluten per kilogram of food, a threshold considered safe for the vast majority of people with celiac disease. Learning to read labels becomes second nature, but the early weeks of diagnosis often involve a steep learning curve around hidden sources of gluten in sauces, seasonings, processed foods, and even items like soy sauce and beer.
Gluten in Medications and Supplements
Concerns about gluten in medications are common but largely overblown. The FDA has found that the vast majority of oral medications in the U.S. contain no gluten or virtually none. No currently marketed oral drug products intentionally include wheat gluten or wheat flour. In the rare cases where wheat starch appears as an ingredient, it would contribute no more than 0.5 mg of gluten per dose, well below the amount found in a single serving of food labeled gluten-free. You can check for yourself by reading the inactive ingredients on nonprescription drug labels or the “Description” section of prescription drug labeling. If wheat gluten or wheat flour isn’t listed, the product is safe for a typical person with celiac disease.
Cross-contamination is often a bigger practical concern than hidden ingredients. Shared toasters, cutting boards, cooking oil used to fry breaded foods, and restaurant kitchens that don’t separate gluten-free preparation areas can all introduce enough gluten to trigger intestinal damage, even without noticeable symptoms. Many people with celiac disease find that dedicated kitchen tools and clear communication at restaurants are essential parts of managing the condition day to day.