Celiac disease triggers an immune attack on the lining of your small intestine every time you eat gluten, a protein found in wheat, barley, and rye. The damage starts in the gut but ripples outward, affecting your bones, blood, skin, nervous system, and reproductive health. About 1 in 100 people worldwide have celiac disease, and many don’t know it because their symptoms show up far from the digestive tract.
What Happens Inside the Small Intestine
Your small intestine is lined with tiny, finger-like projections called villi that absorb nutrients from food. In celiac disease, gluten proteins survive digestion largely intact, arriving in the intestine as large fragments. In people who carry certain genetic markers (called HLA-DQ2 or HLA-DQ8, present in nearly all celiac patients), those fragments set off two overlapping immune responses.
The first response happens in the intestinal lining itself. Immune cells flood the surface layer, directly damaging the cells responsible for absorbing nutrients. The second response occurs in the tissue just beneath that lining, where the immune system generates inflammatory signals that destroy the villi. Over time, the villi flatten and shrink, a process called villous atrophy. With less absorptive surface area, your body struggles to pull essential nutrients from food, no matter how well you eat.
Nutrient Deficiencies and Malabsorption
Because the damage concentrates in the upper part of the small intestine, where most nutrient absorption takes place, celiac disease commonly causes deficiencies in iron, calcium, magnesium, zinc, folate, vitamin D, vitamin B12, niacin, and riboflavin. Protein and calorie absorption can also suffer. These aren’t minor shortfalls. They drive many of the symptoms people experience, from chronic fatigue and brain fog to muscle cramps and easy bruising.
What makes this tricky is that you can be severely malnourished without obvious digestive symptoms. Some people with celiac disease never have diarrhea or stomach pain. Their first clue is a blood test showing iron levels that won’t respond to supplements, or a bone scan revealing unexpected bone loss.
Iron Deficiency Anemia
Anemia is one of the most common ways celiac disease reveals itself outside the gut. The proximal duodenum, the very first section of the small intestine, is where your body absorbs most of its iron. It’s also the region most consistently destroyed in celiac disease. In one study of 434 celiac patients, 39% had anemia as their only presenting symptom. A larger Italian study of over 1,000 patients with subtle or silent celiac disease found iron deficiency anemia in 46% of adults and 35% of children.
If you’ve been told you have unexplained iron deficiency anemia, especially if iron supplements aren’t helping, celiac disease is one of the conditions your doctor should consider.
Bone Loss
Poor absorption of calcium and vitamin D weakens bones over time. Low bone mineral density shows up in 26% to 72% of people at the time they’re first diagnosed with celiac disease, even those who never had digestive complaints. This puts celiac patients at higher risk for osteoporosis and fractures, sometimes decades earlier than expected. In younger patients, it can interfere with building peak bone mass, which has lifelong consequences.
Effects on the Nervous System
Celiac disease can cause neurological problems through two pathways: nutrient deficiencies (particularly B12 and folate) and direct immune-mediated damage. The same antibodies that attack the intestinal lining can also target a related enzyme found throughout the central nervous system. Research has shown these antibodies can trigger nerve cell death.
The most well-documented neurological complication is gluten ataxia, a condition affecting balance and coordination. Up to 70% of patients with gluten ataxia also have slurred speech, involuntary eye movements, and difficulty coordinating their limbs. Peripheral neuropathy, which causes tingling, numbness, or pain in the hands and feet, is another recognized complication. Epilepsy occurs in about 5% of adults with celiac disease, representing a 1.4-fold increased risk compared to the general population. Headaches and cognitive impairment are also reported frequently.
Skin Reactions
Between 10% and 25% of people with celiac disease develop dermatitis herpetiformis, an intensely itchy skin rash. It appears as clusters of small bumps or fluid-filled blisters, often on the elbows, knees, buttocks, and back. The bumps may appear red, purple, or darker than surrounding skin depending on your skin tone. For some people, this rash is the first and most obvious sign of celiac disease, appearing long before any gut symptoms do. It responds to the same treatment as intestinal celiac disease: removing gluten from the diet.
Reproductive Health
Untreated celiac disease can affect fertility and pregnancy in subtle ways. Women with celiac disease tend to start menstruating slightly later and reach menopause earlier, shortening their overall reproductive window. Population data shows that overall fertility rates are similar between women with and without celiac disease, but the timing shifts. Women with celiac disease tend to have lower fertility when younger and relatively higher fertility when older.
Pregnancy carries moderately elevated risks. One large cohort study found a 33% higher rate of cesarean delivery and a 31% higher rate of miscarriage in women with celiac disease. Folate deficiency, common in celiac disease, is a known risk factor for neural tube defects in developing babies. The encouraging finding is that these pregnancy-related risks appear to normalize after successful treatment with a gluten-free diet.
How Diagnosis Works
The preferred initial screening test is a blood test measuring a specific antibody called tTG-IgA. This test is most accurate when you’re still eating gluten regularly. If the blood test is positive, or if clinical suspicion is high even when blood tests are negative, the next step is an upper endoscopy. During this procedure, a doctor takes multiple small tissue samples from the duodenum, typically at least six from different locations, to look for villous atrophy and inflammation under a microscope. A confirmed diagnosis rests on the combination of symptoms, blood work, and biopsy findings.
Recovery on a Gluten-Free Diet
A strict gluten-free diet is the only established treatment. Once gluten is removed, the immune attack stops and the intestinal lining begins to heal, but full recovery takes longer than most people expect. In a study tracking adults with celiac disease after diagnosis, only 34% had confirmed mucosal recovery at 2 years. At 5 years, that number reached 66%. The median time to full intestinal healing was roughly 3.8 years.
Symptoms often improve much faster than the tissue itself heals. Many people feel noticeably better within weeks to months. But the gap between feeling better and being fully healed is important, because ongoing villous atrophy means ongoing malabsorption. This is why strict adherence matters even when you feel fine, and why follow-up blood work and sometimes repeat biopsies are part of long-term management.
Nutrient deficiencies typically improve as the intestine recovers, though some people need targeted supplementation for iron, calcium, vitamin D, or B vitamins in the meantime. Bone density can improve, particularly in younger patients, once absorption normalizes. Neurological symptoms may or may not fully resolve depending on how long the damage has been present before diagnosis.