Celiac disease is an autoimmune condition in which eating gluten triggers your immune system to attack the lining of your small intestine. It affects roughly 1 to 3 percent of the global population, though many cases go undiagnosed for years. The word “celiac” comes from the Greek word for abdomen, but the disease reaches well beyond the gut, causing problems in the bones, skin, nervous system, and blood.
How Gluten Triggers Intestinal Damage
When someone with celiac disease eats gluten, a protein found in wheat, barley, and rye, their immune system treats it as a threat. The resulting attack damages the tiny, fingerlike projections called villi that line the small intestine. Villi are what give the intestine its enormous surface area for absorbing nutrients. As they flatten and erode, the intestine loses its ability to pull vitamins and minerals from food, no matter how much you eat.
This damage reduces absorption of iron, calcium, zinc, folate, vitamin B12, and fat-soluble vitamins like vitamin D. Over months or years, those deficiencies cascade into other problems: anemia from low iron or B12, weakened bones from poor calcium and vitamin D uptake, and chronic fatigue that doesn’t improve with rest.
Who Gets Celiac Disease
Celiac disease is genetic. About 90 percent of people with the condition carry a specific gene variant called HLA-DQ2, while another 5 to 10 percent carry a related variant called HLA-DQ8. Nearly all celiac patients have at least one of these two gene types. Carrying the gene doesn’t guarantee you’ll develop the disease, but without it, celiac is essentially ruled out. This is why testing for these genes can be useful when a diagnosis is uncertain.
The disease runs in families. If a first-degree relative (parent, sibling, or child) has celiac, your risk is significantly higher than the general population’s. It can appear at any age, sometimes triggered by a stressful event, surgery, pregnancy, or infection in someone who was genetically predisposed all along.
Symptoms Beyond the Gut
The classic picture of celiac disease involves diarrhea, bloating, and abdominal pain. But many people, especially adults, never experience obvious digestive symptoms. This is part of why the condition is so frequently missed.
Celiac disease can cause a blistering, intensely itchy skin rash called dermatitis herpetiformis, which typically appears on the elbows, knees, and buttocks. Some people with this rash have no gut symptoms at all despite having the same intestinal damage. Neurological problems are also surprisingly common. Peripheral neuropathy, which causes tingling, numbness, or pain in the hands and feet, affects up to 39 percent of celiac patients and can even appear before any digestive complaints. A condition called gluten ataxia causes progressive problems with balance, coordination, speech, and eye movements.
Other signs include unexplained iron-deficiency anemia, recurring mouth sores, joint pain, and in children, delayed growth or failure to thrive.
How Celiac Disease Is Diagnosed
Diagnosis typically starts with a blood test that measures antibodies your immune system produces in response to gluten. The most common screening test looks for tissue transglutaminase antibodies. Levels below 4 units per milliliter make celiac very unlikely, levels between 4 and 10 fall into a gray zone, and levels above 10 strongly suggest celiac disease. A second antibody test can confirm the result.
If blood work is positive, the next step is usually an intestinal biopsy, where a small tissue sample is taken from the upper small intestine during an endoscopy. Pathologists grade the damage on a scale. Early stages show only increased immune cells in the intestinal lining with the villi still intact. More advanced disease shows the villi progressively flattened, from mildly blunted to completely flat, which represents the most severe damage. You need to be eating gluten regularly before both the blood test and the biopsy, or the results can come back falsely normal.
Celiac Disease vs. Gluten Sensitivity
Not everyone who feels sick after eating gluten has celiac disease. Non-celiac gluten sensitivity causes overlapping symptoms like bloating, fatigue, and brain fog, but it does not produce the specific antibodies found in celiac disease, and it does not cause the characteristic villous damage in the small intestine. People with gluten sensitivity may have some low-level immune activation in their gut, but it’s a fundamentally different process. One key distinction: if genetic testing shows you don’t carry HLA-DQ2 or HLA-DQ8, celiac disease is effectively ruled out, though gluten sensitivity is still possible.
Living Gluten-Free With Celiac Disease
The only current treatment for celiac disease is a strict, lifelong gluten-free diet. This means eliminating all wheat, barley, rye, and any products derived from them. In the United States, foods labeled “gluten-free” must contain less than 20 parts per million of gluten, the threshold the FDA considers safe for people with the condition.
Strict means strict. Even small, repeated exposures can sustain intestinal damage, sometimes without causing noticeable symptoms. This makes cross-contamination a real concern: shared toasters, cutting boards, fryers, and even cosmetics or medications containing gluten can be sources. Most people see significant improvement within weeks to months of removing gluten, though full intestinal healing can take a year or longer.
Nutritional monitoring is an important part of management. Because celiac disease impairs absorption of iron, calcium, folate, zinc, and vitamins D and B12, your levels of these nutrients should be checked and supplemented if needed, especially in the early period after diagnosis.
What Happens if Celiac Goes Untreated
Left untreated, celiac disease can lead to complications that extend far beyond digestive discomfort. Chronic malabsorption weakens bones over time, potentially leading to osteoporosis that may not be fully reversible. Ongoing inflammation raises the risk of infertility in both men and women, and nerve damage from the disease can become permanent. Untreated celiac also increases the risk of developing a type of intestinal lymphoma, though this remains uncommon overall. Lactose intolerance frequently develops as a secondary effect of the damaged intestinal lining, though it often resolves once the gut heals on a gluten-free diet.