Celiac disease is an autoimmune condition where eating gluten triggers your immune system to attack the lining of your small intestine

When you have celiac disease, your body treats gluten—a protein found in wheat, barley, and rye—as a threat. Your immune system responds by attacking the tissue in your small intestine, specifically the finger-like projections called villi that absorb nutrients from food. Over time, this damage reduces how much nutrition your body can take in, even if you eat enough food. The damage is real and measurable on a biopsy, not a sensitivity or preference.

Celiac disease is different from a wheat allergy, which triggers a different immune response, and from non-celiac gluten sensitivity, where people have symptoms but no intestinal damage. With celiac disease, the intestinal damage happens whether or not you feel sick—some people have no symptoms at all, which is why many cases go undiagnosed for years.

Key Takeaways

  • Celiac disease damages the small intestine when you eat gluten, reducing your ability to absorb nutrients like iron, calcium, and B vitamins.
  • The condition is autoimmune, meaning your own immune system causes the damage, and it is permanent—the only treatment is a strict gluten-free diet.
  • You can have celiac disease without symptoms, which means many people are undiagnosed or diagnosed only after years of vague health problems.
  • Intestinal damage from celiac disease can lead to anemia, weak bones, infertility, and neurological problems if left untreated.

How the immune system damages the intestine

Your small intestine is lined with millions of villi—tiny, hair-like structures that increase the surface area for absorbing nutrients. In celiac disease, when gluten enters your digestive tract, your immune system recognizes a protein in gluten called gliadin as dangerous. Your body produces antibodies against gliadin and also against an enzyme in your intestinal lining called tissue transglutaminase (tTG). These antibodies attack the villi, flattening them and causing inflammation.

This attack happens at the cellular level. The immune cells infiltrate the intestinal lining, and the inflammation causes the villi to shrink and eventually flatten. A doctor can see this damage under a microscope on a small intestinal biopsy—the villi go from tall and finger-like to blunt and short, reducing the absorbing surface by up to 90 percent in severe cases. Each time you eat gluten, the cycle repeats, and the damage accumulates.

What happens when nutrients cannot be absorbed

When your intestinal lining is damaged, you cannot absorb nutrients efficiently, even if you eat a balanced diet. This leads to deficiencies in iron, calcium, vitamin B12, folate, fat-soluble vitamins (A, D, E, K), and other essential nutrients. The specific deficiencies depend on how much damage you have and how long the damage has been happening.

Iron deficiency is one of the most common results, leading to anemia—low red blood cell count—which causes fatigue, shortness of breath, and pale skin. Calcium and vitamin D deficiencies weaken bones, increasing the risk of osteoporosis and fractures, especially in children whose bones are still developing. Vitamin B12 and folate deficiencies can cause neurological symptoms like numbness, tingling, and difficulty concentrating. Some people develop dermatitis herpetiformis, a blistering skin rash caused by gluten, which is a sign of intestinal damage even without digestive symptoms.

Symptoms vary widely or may not appear at all

Celiac disease presents differently in different people. Some experience classic digestive symptoms: chronic diarrhea, constipation, bloating, gas, and abdominal pain. Others have no digestive symptoms at all but instead develop anemia, fatigue, joint pain, headaches, or depression. Children may fail to grow at a normal rate or develop behavioral problems. Some people have no symptoms and discover they have celiac disease only when screened for other reasons or when a family member is diagnosed.

The lack of symptoms does not mean the intestine is not being damaged. Silent celiac disease—where damage is present but the person feels fine—is common. This is why screening is important for people with a family history of celiac disease, even if they feel healthy. The longer undiagnosed celiac disease goes untreated, the greater the risk of serious complications.

Long-term complications if left untreated

Untreated celiac disease can lead to serious health problems over months or years. Severe malnutrition can cause growth delays in children and permanent neurological damage. Osteoporosis develops when calcium and vitamin D deficiencies weaken bones, making fractures more likely. Some people develop infertility or repeated miscarriages due to nutritional deficiencies and intestinal inflammation.

There is also an increased risk of certain cancers, particularly intestinal lymphoma, in people with untreated celiac disease. Dermatitis herpetiformis, the gluten-related skin rash, can cause intense itching and scarring. Additionally, untreated celiac disease is associated with increased rates of depression, anxiety, and other mental health conditions, partly due to nutritional deficiencies and partly due to chronic inflammation. The good news is that these complications are preventable with a gluten-free diet, and many reverse if you stop eating gluten before permanent damage occurs.

How celiac disease is diagnosed

Diagnosis requires two steps: blood tests and, usually, a small intestinal biopsy. Blood tests look for antibodies your body produces against gluten and against tissue transglutaminase (tTG). The most common tests are tissue transglutaminase IgA (tTG-IgA) and endomysial antibodies (EMA). These antibodies are only present if you are eating gluten regularly, so you must not start a gluten-free diet before testing—doing so will make the tests negative even if you have celiac disease.

If blood tests are positive, your doctor will refer you to a gastroenterologist, who performs an upper endoscopy to take small samples of tissue from your small intestine. A pathologist examines these samples under a microscope to confirm intestinal damage. This biopsy is the gold standard for diagnosis because it shows the actual damage and rules out other conditions. In rare cases, a person may be diagnosed based on blood tests alone if the antibody levels are very high and symptoms are classic, but a biopsy is standard practice.

The gluten-free diet is the only treatment

There is no medication that cures celiac disease or allows you to eat gluten safely. The only treatment is a strict, lifelong gluten-free diet—avoiding all wheat, barley, rye, and foods made from these grains. This means no regular bread, pasta, cereals, baked goods, or many processed foods. Cross-contamination matters: even crumbs from regular bread or a shared toaster can trigger an immune response in some people.

When you stop eating gluten, your immune system stops attacking your intestine. The inflammation decreases within days, and the villi begin to heal. Most people feel better within weeks, though complete healing of the intestinal lining can take months or even years, especially in adults. Once healed, your intestine can absorb nutrients normally again, and deficiencies can be corrected. Many people need to work with a dietitian who specializes in celiac disease to learn which foods are safe and how to avoid hidden sources of gluten in processed foods, sauces, and medications.

Frequently Asked Questions

Can celiac disease develop at any age?

Yes. Celiac disease can appear in childhood, adolescence, or adulthood. Some people are diagnosed in their 60s or 70s. Pregnancy, surgery, stress, or infection can sometimes trigger the onset of symptoms in someone who carries the genetic predisposition. You are not born with active celiac disease; you are born with the genes that make it possible, and something must trigger it.

If my parent has celiac disease, will I definitely get it?

No. Celiac disease runs in families because it requires specific genes, but having the genes does not may provide you will develop the disease. About 30 to 40 percent of people carry the genes associated with celiac disease, but only 2 to 3 percent of the general population actually has it. If a close relative has celiac disease, you have a higher risk and may want to be screened, especially if you have symptoms or other autoimmune conditions.

Does a gluten-free diet heal the intestine completely?

In most cases, yes. The intestinal lining usually heals within weeks to months of starting a strict gluten-free diet, and villi return to normal. However, healing takes longer in adults than in children, and some people with severe, long-standing damage may have incomplete healing. Once healed, the intestine can absorb nutrients normally, and most complications reverse or improve significantly.

Can I have celiac disease if I feel fine?

Yes. Many people have celiac disease without any noticeable symptoms. The intestine is still being damaged, and deficiencies are still developing, even if you feel well. This is why screening is recommended for people with a family history of celiac disease or certain other autoimmune conditions, regardless of symptoms.

Is celiac disease the same as a gluten allergy?

No. Celiac disease is autoimmune—your immune system attacks your own intestinal tissue. A wheat allergy is a different immune response where your body reacts to wheat proteins as if they were a threat, causing symptoms like hives, swelling, or anaphylaxis. A wheat allergy can be life-threatening; celiac disease is not, but untreated celiac disease causes long-term damage.