What Underlying Conditions Cause Low Iron? An Expert Guide

October 7, 2025 •

3 min read

Globally, iron deficiency is the most common cause of anemia, affecting millions. While inadequate dietary intake is a factor, low iron is often a symptom of a deeper, underlying medical issue. Understanding what underlying conditions cause low iron is the first step toward proper diagnosis and effective treatment.

Quick Summary

Low iron is often caused by various underlying conditions, including chronic blood loss, impaired iron absorption, and long-term inflammation from chronic diseases. Treating the root cause is critical for successful long-term management of the deficiency.

Key Points

Blood Loss is Common: In developed countries, chronic blood loss, often from the GI tract or heavy menstruation, is the leading cause of low iron.
Absorption is Key: Conditions like Celiac disease and gastric surgeries can severely impair the body's ability to absorb iron from food.
Inflammation's Role: Chronic inflammatory diseases such as rheumatoid arthritis and kidney disease interfere with the body's iron metabolism.
Infections are a Factor: Globally, parasitic infections like hookworm and malaria are significant contributors to low iron and anemia.
Diagnosis is Essential: Self-treating is not recommended. A medical diagnosis with tests like a ferritin level is necessary to uncover the root cause.
Address the Root Cause: Effective treatment for iron deficiency depends on addressing the specific underlying condition rather than just supplementing iron.

Chronic Blood Loss: The Primary Culprit

In developed countries, the most common reason for low iron is often chronic, internal blood loss, which can be easily overlooked. As red blood cells contain iron, losing blood means losing iron. This slow, persistent loss can gradually deplete the body's iron stores without any dramatic, visible bleeding.

Gastrointestinal (GI) Bleeding

Many conditions can cause chronic GI bleeding, leading to low iron. These include:

Peptic ulcers: Sores on the lining of the stomach or small intestine.
Hiatal hernia: A condition where part of the stomach pushes up through the diaphragm.
Colon polyps or colorectal cancer: Growths in the large intestine that can bleed slowly.
Regular use of pain relievers: Frequent use of NSAIDs like aspirin or ibuprofen can cause GI tract bleeding.

Heavy Menstruation

For premenopausal women, heavy menstrual bleeding is a very common cause of iron deficiency. Some women may not realize just how much blood they are losing each month, and this cumulative loss over time can significantly reduce iron levels.

Frequent Blood Donation

People who donate blood regularly may be at a higher risk of developing iron deficiency, as each donation removes iron from the body.

Impaired Iron Absorption: Malabsorption Conditions

Even with sufficient iron in the diet, certain conditions can prevent the body from properly absorbing it in the small intestine, leading to a deficiency.

Celiac Disease

This autoimmune disorder is triggered by consuming gluten. It causes damage to the lining of the small intestine, impairing its ability to absorb iron and other nutrients effectively.

Intestinal or Gastric Surgery

Procedures such as gastric bypass or the removal of part of the small intestine can affect the body's ability to absorb iron and other nutrients, increasing the risk of deficiency.

Helicobacter pylori Infection

An infection with the bacteria H. pylori can cause atrophic gastritis, which reduces stomach acid needed for iron absorption.

Chronic Diseases and Inflammation

Long-standing inflammatory conditions can interfere with the body's iron regulation, a phenomenon known as "anemia of inflammation" or "anemia of chronic disease".

Chronic Kidney Disease

Individuals with kidney disease often don't produce enough erythropoietin, a hormone the body needs to make red blood cells.

Autoimmune and Inflammatory Conditions

Diseases such as rheumatoid arthritis, inflammatory bowel disease (Crohn's or ulcerative colitis), and congestive heart failure can cause persistent inflammation that affects iron metabolism.

Other Significant Causes

Beyond the most common culprits, several other factors can contribute to low iron levels.

Pregnancy

Increased blood volume and the developing fetus's demand for hemoglobin place a higher iron requirement on pregnant individuals, often leading to iron deficiency without supplementation.

Infections

In many parts of the world, infections are a major cause of anemia. Malaria, hookworm, and schistosomiasis can cause blood loss or impair nutrient absorption.

Rare Genetic Conditions

Some rare genetic conditions can directly impact iron absorption or lead to chronic blood loss.

Comparison of Underlying Causes of Low Iron


Cause Category	Mechanism	Common Examples
Chronic Blood Loss	Gradual loss of blood and, therefore, iron over time.	Heavy menstrual bleeding, bleeding ulcers, NSAID use, frequent blood donation, GI cancers.
Impaired Absorption	The body cannot absorb iron from food effectively due to intestinal damage or surgery.	Celiac disease, Crohn's disease, gastric bypass surgery, H. pylori infection.
Inflammation	Long-term inflammation interferes with the body's iron regulation and red blood cell production.	Chronic kidney disease, rheumatoid arthritis, heart failure, inflammatory bowel disease.

When to Seek Medical Attention

Symptoms of low iron, such as fatigue, dizziness, and shortness of breath, are often non-specific and can overlap with other conditions. It is crucial to consult a healthcare provider for a proper diagnosis rather than self-treating. Blood tests, including a ferritin level test, are the most reliable way to confirm an iron deficiency. A medical professional can then help identify the specific underlying cause and recommend the most effective treatment plan, which may involve treating the root condition, taking supplements, or making dietary changes.

Conclusion

Low iron is not always a simple dietary issue; it is frequently a critical indicator of an underlying health problem. From hidden blood loss in the gastrointestinal tract to autoimmune disorders and chronic infections, the potential causes are varied and require careful investigation. By understanding these diverse origins, individuals can work with their healthcare providers to get an accurate diagnosis. Addressing the root cause is the key to resolving iron deficiency, restoring optimal health, and preventing recurrence. For more comprehensive information, the National Institutes of Health provides valuable resources on iron deficiency anemia.

Frequently Asked Questions

The most common underlying cause of low iron in many populations is chronic blood loss, which can occur from heavy menstrual periods or slow bleeding in the gastrointestinal tract due to conditions like ulcers or colon polyps.

Yes, Celiac disease can cause low iron by damaging the lining of the small intestine. This damage impairs the body's ability to absorb iron from digested food, leading to a deficiency even with adequate dietary intake.

Chronic inflammation, often from diseases like rheumatoid arthritis or kidney disease, interferes with the body's iron regulation. The body's immune response can disrupt how iron is stored and used, leading to what is known as anemia of chronic disease.

No, low iron (or iron-deficiency anemia) is considered a symptom or indicator of an underlying condition rather than a disease itself. For effective treatment, it is critical to identify and address the root cause.

Yes, gastrointestinal bleeding can be a silent or 'occult' cause of low iron. It can be caused by conditions such as a bleeding ulcer, colon polyps, or regular use of NSAID pain relievers, with bleeding being so slow that it goes unnoticed.

It is important to see a doctor for low iron because self-treatment can mask a more serious underlying condition. A healthcare provider can run tests to confirm the diagnosis and investigate potential root causes like internal bleeding or chronic disease, leading to a more targeted and effective treatment plan.

During pregnancy, the body's blood volume increases, and iron is needed for both the mother and the developing fetus. This higher demand for iron often leads to deficiency if not managed with dietary changes or supplementation.