What illness can cause low iron levels? A comprehensive guide

November 22, 2025 •

4 min read

According to the World Health Organization, anemia affects billions globally, often due to low iron. Beyond diet, a variety of underlying illnesses can cause low iron levels by affecting absorption, storage, or causing chronic blood loss.

Quick Summary

Several medical conditions, including chronic inflammatory diseases, gastrointestinal disorders, and kidney disease, can lead to low iron levels.

Key Points

Anemia of Inflammation: Chronic diseases like rheumatoid arthritis, lupus, and infections cause inflammation that traps iron in storage, making it unavailable for red blood cell production.
Gastrointestinal Disorders: Conditions such as Celiac disease, Crohn's, and ulcerative colitis can prevent the body from absorbing iron properly from food.
Occult Blood Loss: Many GI issues, including ulcers and colon cancer, can cause slow, unnoticeable bleeding that steadily depletes iron reserves.
Chronic Kidney Disease: Damaged kidneys produce less of the hormone erythropoietin and also trigger inflammation that locks up iron stores.
Diagnosis is Key: Low iron levels can be a sign of a more serious underlying illness, and simply taking iron supplements may not address the root cause.

Anemia of Chronic Inflammation

This condition, also known as anemia of chronic disease (ACD), is the second most common type of anemia after iron deficiency anemia (IDA). It occurs in people with long-term illnesses that cause inflammation, which interferes with the body's iron metabolism. Instead of being available for making new red blood cells, iron becomes trapped in storage cells (macrophages), even if the body has normal or even high iron stores.

Autoimmune Diseases

Autoimmune disorders are a major trigger for ACD. Conditions like rheumatoid arthritis and systemic lupus erythematosus (lupus) cause chronic inflammation that leads to anemia. The body's immune response releases inflammatory proteins called cytokines, which prevent the bone marrow from efficiently producing new red blood cells and cause iron sequestration.

Chronic Infections

Persistent infections, such as HIV/AIDS, tuberculosis, and chronic viral infections, can also induce a state of inflammation that results in ACD. The inflammatory response is designed to fight the infection, but its side effect is disrupted iron usage, leading to a functional iron deficiency where iron is present but inaccessible.

Cancer and Malignancy

Various cancers can induce ACD by causing systemic inflammation. Additionally, cancer treatments like chemotherapy and radiation can further contribute to anemia by suppressing bone marrow function.

Gastrointestinal Disorders

Many digestive diseases are significant causes of low iron, either by impairing absorption or causing chronic blood loss.

Malabsorption Syndromes

These conditions interfere with the body’s ability to absorb iron from food, as the main site of absorption is the small intestine.

Celiac Disease: This autoimmune disorder damages the lining of the small intestine when gluten is consumed. This damage, particularly in the duodenum where iron is absorbed, severely hinders nutrient uptake. Iron deficiency is often the presenting sign of celiac disease, even without typical digestive symptoms.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis cause inflammation and damage to the digestive tract. This can lead to malabsorption of iron and other nutrients, and also cause blood loss through ulcers.
Gastric Surgery: Procedures that alter the stomach or small intestine, such as bariatric surgery, can reduce iron absorption.
H. Pylori Infection: This common bacterial infection of the stomach can cause inflammation and ulcers, leading to blood loss and reduced iron absorption.

Gastrointestinal Blood Loss

Slow, chronic bleeding from the digestive tract can gradually deplete the body's iron stores without causing obvious symptoms like visible blood in stool.

Peptic Ulcers: Sores in the stomach or small intestine can bleed, leading to chronic iron loss.
Colon Polyps and Cancer: Tumors in the GI tract can cause slow, occult bleeding that reduces iron levels over time. A workup for low iron often includes a colonoscopy for this reason.
Medication Use: Regular, long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or aspirin can cause stomach irritation and chronic bleeding.

Chronic Kidney Disease

Anemia is a very common complication of chronic kidney disease (CKD), and low iron levels are a major contributor. The kidneys play two critical roles that are disrupted in CKD:

Reduced Hormone Production: Damaged kidneys produce less erythropoietin (EPO), a hormone that signals the bone marrow to create red blood cells.
Functional Iron Deficiency: Inflammation associated with CKD increases the hormone hepcidin, which prevents the body from properly using stored iron.

A Comparison of Low Iron Anemia Causes

To help differentiate between different sources of low iron, a comparison can be helpful. This table contrasts Iron Deficiency Anemia (IDA) due to dietary issues or simple blood loss with Anemia of Chronic Disease (ACD).


Feature	Iron Deficiency Anemia (IDA)	Anemia of Chronic Disease (ACD)
Underlying Cause	Inadequate iron intake, absorption issues, or blood loss	Chronic inflammation from an underlying disease
Iron Stores (Ferritin)	Very low or depleted	Normal to high, but iron is 'sequestered'
Serum Iron Levels	Low	Low
Total Iron Binding Capacity (TIBC)	High, as the body tries to maximize iron uptake	Low or normal, due to inflammation
Response to Oral Iron	Typically effective	Often ineffective due to hepcidin blocking absorption

Conclusion

While a low-iron diet or chronic blood loss are common causes of low iron, several serious illnesses can also be to blame. Anemia of chronic disease (ACD) stems from long-term inflammation, trapping iron and impairing red blood cell production. Gastrointestinal disorders like celiac disease and IBD can cause malabsorption or slow, persistent bleeding. Finally, chronic kidney disease disrupts both iron metabolism and the hormone production needed for red blood cells. For this reason, a finding of low iron should prompt a full medical evaluation to uncover and treat the root cause, rather than simply relying on supplements.

Further reading on anemia and its causes can be found at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

Frequently Asked Questions

Iron deficiency anemia (IDA) is caused by a lack of iron in the body's stores. Anemia of chronic disease (ACD) occurs due to chronic inflammation, which prevents the body from properly using the iron it has stored, even when total body iron is adequate.

Yes, Celiac disease is a major cause of low iron. The condition damages the lining of the small intestine, specifically the duodenum, which is where iron is absorbed. This leads to malabsorption and iron deficiency.

These illnesses cause chronic inflammation. The body's immune response produces cytokines and other proteins that lead to a 'functional' iron deficiency by trapping iron in storage cells (macrophages) and limiting its use for creating red blood cells.

Yes, chronic kidney disease is a common cause. It reduces the kidney's production of the hormone erythropoietin, which signals the bone marrow to produce red blood cells. Inflammation related to CKD also hinders iron metabolism.

Conditions like peptic ulcers, chronic gastritis, inflammatory bowel disease (Crohn's and ulcerative colitis), and gastrointestinal cancers can cause slow, persistent bleeding that depletes the body's iron stores over time.

Yes, some medications can cause low iron levels. For example, long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin or ibuprofen can cause gastrointestinal bleeding.

It depends on the illness. For simple iron deficiency, supplements are often effective. However, with anemia of chronic disease, the iron is trapped in stores, so supplements may not be absorbed or used properly due to the inflammation. Treating the underlying condition is the primary approach.