What are the causes of iron deficiency anemia?

October 11, 2025 •

4 min read

Worldwide, iron deficiency is the most common nutritional disorder, affecting an estimated 30% of the population with iron deficiency anemia (IDA). This condition occurs when the body lacks enough iron to produce hemoglobin, the protein in red blood cells that carries oxygen. Understanding the various causes is crucial for effective prevention and treatment of iron deficiency anemia.

Quick Summary

This article explores the primary culprits behind iron deficiency anemia, detailing the roles of blood loss, inadequate dietary intake, poor iron absorption, and increased iron demands. It provides an overview of associated medical conditions and offers a comparison of key contributing factors.

Key Points

Blood Loss is a Primary Culprit: In adults, chronic internal bleeding from ulcers, NSAID use, or gynecological issues like heavy periods is the most frequent cause of iron deficiency.
Diet and Absorption Play Major Roles: Inadequate intake of iron, especially from sources like red meat, or consuming foods that block iron absorption (e.g., coffee, tea) are significant factors.
Certain Medical Conditions Inhibit Absorption: Diseases affecting the small intestine, like celiac disease or Crohn's disease, and procedures like bariatric surgery, can severely limit iron uptake from food.
Higher Needs Increase Vulnerability: Pregnant women, infants, growing adolescents, and endurance athletes have higher iron demands that can outpace their intake, making them susceptible to deficiency.
Treatment Addresses the Root Cause: Effective treatment for iron deficiency anemia involves not only replenishing iron stores with supplements but also identifying and managing the underlying issue, such as controlling bleeding or correcting malabsorption.

Blood Loss: The Primary Cause

In adults, especially men and postmenopausal women, the most common cause of iron deficiency anemia is chronic blood loss. The body loses iron when it loses blood, and if this loss is sustained, iron stores become depleted.

Gastrointestinal Bleeding

Many common health issues can lead to slow, ongoing blood loss in the digestive tract, which can go unnoticed for long periods.

Peptic ulcers: Sores in the lining of the stomach or small intestine can bleed slowly over time.
Regular NSAID use: Over-the-counter pain relievers like aspirin and ibuprofen can irritate the stomach lining and cause bleeding.
Colon polyps and cancer: Growths in the large intestine can be a source of chronic, low-volume blood loss.
Inflammatory bowel diseases (IBD): Conditions like Crohn's disease and ulcerative colitis cause inflammation and bleeding in the intestines.

Gynecological and Obstetric Blood Loss

Women of childbearing age are at a significantly higher risk for iron deficiency due to blood loss from menstruation and pregnancy.

Heavy menstrual bleeding (menorrhagia): This is a very common cause of iron deficiency in women and adolescent girls.
Pregnancy and childbirth: The body’s iron requirements increase substantially during pregnancy to support the increased blood volume and provide for the developing fetus. Postpartum hemorrhage can also contribute to iron loss.

Other Sources of Blood Loss

Other, less common sources of bleeding can also deplete the body's iron supply.

Frequent blood donation: Regular donors may be at a higher risk of iron deficiency and should be monitored.
Urinary tract bleeding: Though rare, blood loss can occur from the kidneys or bladder.

Dietary and Nutritional Factors

While less common in developed nations, inadequate dietary iron intake can be a primary cause of iron deficiency, especially in vulnerable populations.

Insufficient Iron Intake

Not consuming enough iron-rich foods is a direct path to deficiency.

Vegetarian and vegan diets: Since heme iron from animal products is absorbed more efficiently than non-heme iron from plants, those who exclude meat must be careful to consume sufficient plant-based sources and iron absorption enhancers.
Poor overall diet: Individuals with limited access to nutritious food or those on highly restrictive diets may not get enough iron.

Factors Inhibiting Absorption

Some dietary and lifestyle factors can actively hinder the body's ability to absorb iron, even with an adequate intake.

Tea and coffee: These beverages contain polyphenols that significantly inhibit non-heme iron absorption and should not be consumed with iron-rich meals.
High-calcium foods and supplements: Calcium can interfere with iron absorption, so it's recommended to take calcium supplements and iron supplements at separate times.
Phytates: Found in whole grains, cereals, and legumes, phytates can also reduce iron absorption.

Impaired Iron Absorption (Malabsorption)

Even with a balanced diet, certain medical conditions can prevent the body from absorbing iron properly.

Celiac disease: This autoimmune disorder damages the lining of the small intestine, the site where most iron is absorbed.
Helicobacter pylori (H. pylori) infection: This bacterial infection can cause atrophic gastritis, which reduces stomach acid needed for iron absorption.
Bariatric surgery: Procedures like gastric bypass can bypass parts of the small intestine where iron is absorbed, leading to long-term malabsorption.
Chronic kidney disease (CKD): In addition to issues with iron regulation, some patients with CKD, especially those on dialysis, can develop iron deficiency.

Increased Iron Demands

Sometimes, the body's need for iron simply outpaces its intake and absorption, even with no blood loss.

Pregnancy: As noted, pregnancy significantly increases iron requirements to support the mother and fetus.
Growth spurts in children and adolescents: Rapid growth phases require extra iron for new blood cells and expanding muscle mass.
Intense athletic training: Endurance athletes, particularly female runners, can experience increased iron loss through sweating and micro-hemorrhages in the GI tract.

Comparison of Major Causes of Iron Deficiency Anemia


Cause Category	Primary At-Risk Population	Mechanism of Deficiency	Key Examples
Chronic Blood Loss	Adult males, postmenopausal women, menstruating women, NSAID users	Steady loss of iron-rich blood over time.	Gastrointestinal bleeding (ulcers, polyps), heavy menstruation.
Poor Dietary Intake	Vegetarians, vegans, pregnant women, infants	Insufficient consumption of iron or high intake of absorption blockers.	Lack of red meat, excess tea/coffee with meals.
Malabsorption	Post-surgery patients, celiac disease patients, IBD patients	Conditions preventing the small intestine from properly absorbing iron.	Bariatric surgery, celiac disease.
Increased Demand	Pregnant women, adolescents, endurance athletes	Body's need for iron exceeds normal intake during periods of growth or high activity.	Pregnancy, puberty, intense endurance training.

Conclusion

Understanding the diverse causes of iron deficiency anemia is the first step toward effective management and prevention. Whether stemming from chronic blood loss, dietary inadequacies, malabsorption issues, or increased physiological demands, the root cause must be identified to create a targeted treatment plan. For some, simple dietary adjustments can suffice, while others may require supplements, treatment for an underlying medical condition, or even more intensive therapies. Consulting a healthcare provider for an accurate diagnosis and personalized guidance is essential. A comprehensive approach, considering diet, lifestyle, and medical history, offers the best path to restoring healthy iron levels and overall well-being. Ultimately, addressing the cause, not just the low iron levels, is key to long-term resolution.

Frequently Asked Questions

In adults, chronic blood loss is the most common cause. This can result from gastrointestinal bleeding due to ulcers, polyps, or cancer, or from heavy menstrual bleeding in women.

Yes, following a vegetarian or vegan diet can put you at higher risk for iron deficiency because plant-based non-heme iron is less easily absorbed by the body compared to heme iron found in meat. Careful meal planning with iron-rich plant foods and vitamin C is necessary.

Pregnancy increases a woman's iron needs dramatically to support her own expanded blood volume and provide for the developing fetus. Without sufficient iron intake or supplements, iron stores can become depleted, leading to anemia.

Yes, conditions that affect the small intestine, such as celiac disease and inflammatory bowel diseases like Crohn's disease, can impair the body's ability to absorb iron from food.

Regular, long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen can cause bleeding in the stomach or intestines, leading to chronic blood loss and subsequent iron deficiency.

To improve absorption, pair iron-rich foods with vitamin C sources (e.g., oranges, bell peppers, broccoli). Avoid drinking tea, coffee, or consuming high-calcium foods with meals, as these can inhibit iron absorption.

Groups at the highest risk include young children, menstruating and pregnant women, vegetarians/vegans, and individuals with chronic diseases or gastrointestinal issues causing bleeding or malabsorption.