Celiac disease causes a wide range of symptoms, from chronic diarrhea and bloating to less obvious signs like anemia, skin rashes, and problems with balance. It affects between 0.7% and 2.9% of the global population, and many people go years without a diagnosis because their symptoms don’t look like a “typical” digestive problem.
The disease is an autoimmune reaction to gluten, a protein found in wheat, rye, and barley. When someone with celiac disease eats gluten, their immune system attacks the lining of the small intestine, gradually flattening the tiny finger-like projections (villi) that absorb nutrients from food. That damage is what drives the symptoms, and it explains why celiac disease can affect so many different parts of the body.
Digestive Symptoms in Adults
The digestive symptoms most adults experience include diarrhea, bloating and gas, belly pain, nausea and vomiting, constipation, fatigue, and weight loss. These can range from mild and intermittent to severe enough to disrupt daily life. Some people have loose, pale, foul-smelling stools that float, a sign that fat isn’t being absorbed properly.
What surprises many people is that constipation is just as common as diarrhea in celiac disease. The assumption that celiac always means frequent loose stools leads some people and even some clinicians to overlook it. Fatigue and unexplained weight loss are also core symptoms, not side effects. They result directly from the intestine’s reduced ability to pull nutrients from food.
Symptoms That Have Nothing to Do With Digestion
Many adults with celiac disease present with symptoms outside the gut, and in some cases, these are the only symptoms they notice. Anemia is the second most common way celiac disease shows up in adults, occurring in roughly 15% of people at diagnosis. Iron deficiency is the usual cause, though folate and vitamin B12 deficiencies also play a role. In fact, guidelines in both the US and UK recommend that anyone with unexplained iron-deficiency anemia be tested for celiac disease. Studies of patients undergoing endoscopy for iron-deficiency anemia have found celiac disease in up to 8.7% of them.
A skin condition called dermatitis herpetiformis is one of the most distinctive signs. It causes intensely itchy clusters of small blisters and raised bumps, primarily on the elbows, knees, buttocks, and lower back. This rash is directly caused by the same immune response that damages the intestine, and it’s considered strong enough evidence on its own to prompt celiac testing. The rash can take months to clear on a gluten-free diet, and some people need medication to get relief faster.
Neurological symptoms are more common than most people realize. Gluten ataxia, which causes problems with balance, coordination, and gait, accounts for roughly half of all neurological presentations of celiac disease. It happens because antibodies triggered by gluten cross-react with cells in the cerebellum, the part of the brain that controls movement. Over time, untreated celiac disease can also cause nerve damage in the hands and feet, leading to tingling, numbness, or pain.
How Celiac Disease Looks Different in Children
Children with celiac disease are more likely than adults to have prominent digestive symptoms. The classic picture includes chronic diarrhea, a visibly swollen belly, nausea and vomiting, gas, constipation, and pale or foul-smelling stools. In infants, failure to thrive (not gaining weight or growing as expected) can be an early red flag.
Beyond the gut, children may show slowed growth and short stature compared to their peers, moodiness and irritability that seems out of proportion to circumstances, and damage to the enamel of their permanent teeth. Dental enamel defects can appear as brown, white, or yellow spots and may show up before other symptoms become obvious. Delayed puberty is another sign that sometimes gets attributed to normal variation when celiac disease is actually the cause.
Why Symptoms Vary So Much
The intestinal damage in celiac disease develops gradually. The immune response involves both a targeted attack on the intestinal lining and a broader autoimmune reaction that produces specific antibodies against the body’s own tissues. This means the severity of symptoms depends partly on how much of the intestine is damaged and partly on which nutrients are no longer being absorbed properly.
Someone whose damage primarily blocks iron absorption may show up with anemia and fatigue but no diarrhea. Someone whose calcium absorption is impaired may develop bone thinning years before digestive symptoms appear. The autoimmune antibodies can also deposit in the skin (causing dermatitis herpetiformis) or affect the brain (causing ataxia), which is why the disease looks so different from person to person. Some people with confirmed celiac disease have no noticeable symptoms at all, a form sometimes called “silent” celiac disease, even though intestinal damage is still occurring.
Celiac Disease vs. Gluten Sensitivity
Non-celiac gluten sensitivity can cause many of the same symptoms: belly pain, fatigue, gas, diarrhea, constipation, headaches, joint pain, and rashes. The key difference is that gluten sensitivity does not damage the small intestine. It also doesn’t produce the specific antibodies found in celiac disease. Because the symptoms overlap so heavily, testing for celiac disease (through blood tests and, if needed, intestinal biopsies) should come before anyone assumes their problem is gluten sensitivity. Removing gluten from your diet before testing can make celiac disease harder to detect, since the immune response and intestinal damage begin to heal once gluten is gone.
What Happens if Celiac Disease Goes Untreated
Left unmanaged, celiac disease can lead to complications that go well beyond digestive discomfort. Ongoing nutrient malabsorption can cause significant bone loss, and some of that bone damage may not be fully reversible. Lactose intolerance commonly develops because the damaged intestinal lining loses its ability to process dairy sugars. Infertility can occur in both men and women. Nerve damage may progress and become permanent.
How Celiac Disease Is Diagnosed
Diagnosis typically starts with a blood test that looks for specific antibodies your immune system produces in response to gluten. If those antibody levels are elevated, the next step is usually an upper endoscopy, where small tissue samples are taken from the small intestine to check for the characteristic damage: flattened villi and an increase in immune cells in the intestinal lining. In some cases, when the initial blood test shows antibody levels greater than 10 times the normal threshold and a second blood sample confirms the result with a different antibody test, a diagnosis can be made without a biopsy. This approach is used more often in children. The important thing is to keep eating gluten until testing is complete, since going gluten-free early can cause both blood tests and biopsies to come back falsely normal.