Celiac disease is an autoimmune condition where ingesting gluten triggers an immune response that damages the lining of the small intestine. Anemia, defined by a reduced number of red blood cells or low hemoglobin, is a frequent manifestation of undiagnosed celiac disease. For many adults, chronic, unexplained anemia is the only apparent symptom. Celiac disease causes anemia because the intestinal damage prevents the absorption of micronutrients required for healthy blood production.
How Celiac Disease Impairs Nutrient Absorption
The small intestine is lined with microscopic, finger-like projections called villi, which absorb nutrients from digested food into the bloodstream. Villi dramatically increase the surface area for nutrient uptake, allowing efficient absorption of sugars, fats, vitamins, and minerals. In a person with celiac disease, the immune system mistakes gluten for a threat and attacks the intestinal wall.
This sustained immune response causes the villi to become flattened and damaged, a process known as villous atrophy. The destruction of the villi transforms the highly-folded absorptive surface into a smooth landscape with significantly reduced capacity. When the surface area is compromised, the body cannot efficiently extract nutrients, leading to widespread malabsorption. This failure to absorb nutrients is the direct link between celiac disease and nutritional deficiencies that cause anemia.
Specific Nutritional Deficiencies that Cause Anemia
Anemia resulting from celiac disease is most frequently microcytic anemia, characterized by smaller-than-normal red blood cells. This presentation is caused by an iron deficiency. Iron is a structural component of hemoglobin, the protein in red blood cells that transports oxygen throughout the body.
The duodenum and proximal jejunum, the first sections of the small intestine, are the primary sites for iron absorption. Since celiac disease-related damage often concentrates severely in these upper parts of the intestine, iron malabsorption occurs early and intensely. In some studies, iron deficiency anemia (IDA) is present in over 80% of adult patients at the time of diagnosis, often being the sole presenting sign.
Celiac disease can also cause macrocytic anemia, where red blood cells are abnormally large. This type is caused by deficiencies in vitamin B12 or folate. Folate is absorbed in the same upper regions as iron, making its deficiency relatively common, occurring in about 10% of cases at diagnosis. Vitamin B12 absorption, however, occurs further down in the ileum, so its deficiency is typically seen in cases where the disease is more extensive or has been untreated for a longer duration.
Diagnosis and Resolution of Celiac-Related Anemia
Persistent or unexplained anemia, especially iron deficiency anemia that does not improve with oral iron supplements, indicates that testing for celiac disease is warranted. Diagnosis typically begins with a blood test to check for specific autoantibodies, such as tissue transglutaminase (tTG-IgA), which are markers of the immune reaction to gluten.
If blood tests are positive, a definitive diagnosis requires an upper endoscopy to obtain small tissue samples from the small intestine. This biopsy allows a pathologist to confirm the presence and severity of villous atrophy. Once the link between the anemia and celiac disease is confirmed, the resolution is achieved by adopting a strict, lifelong gluten-free diet (GFD).
The complete removal of gluten halts the autoimmune attack, allowing the small intestine’s villi to gradually heal and regenerate. As the mucosal surface area is restored, the body’s ability to absorb iron, folate, and B12 returns to normal. During this healing phase, which can take several months, high-dose oral or sometimes injected supplementation of the deficient nutrients is often necessary to replenish the body’s reserves and correct the anemia.