What is the main cause of IDA?

December 10, 2025 •

3 min read

According to the World Health Organization, iron deficiency is the most common nutritional deficiency globally. The main cause of IDA, or iron deficiency anemia, varies by population but is overwhelmingly driven by an imbalance where the body loses or demands more iron than it absorbs.

Quick Summary

This article explores the primary drivers of iron deficiency anemia, highlighting blood loss, poor diet, and malabsorption issues as the most frequent culprits. It details how these factors disrupt the body's iron balance and examines specific risk groups and medical conditions.

Key Points

Blood Loss is Primary: The leading cause of IDA in adults is often chronic, low-grade bleeding, particularly from the gastrointestinal tract in men and postmenopausal women.
Menstruation in Women: Heavy menstrual periods are the most common cause of IDA in premenopausal women.
Malabsorption Conditions: Disorders such as celiac disease and inflammatory bowel disease can prevent the body from absorbing enough iron, even with a balanced diet.
Increased Demand: Life stages with high growth rates, such as pregnancy, infancy, and adolescence, increase iron requirements and the risk of IDA.
Treatment Focus: Effective treatment of IDA requires addressing the underlying cause, not just providing iron supplements.

Understanding the Core Mechanisms of Iron Deficiency Anemia

Iron deficiency anemia (IDA) occurs when the body's iron stores become too depleted to support the production of healthy red blood cells. Red blood cells use a protein called hemoglobin to carry oxygen throughout the body. Without sufficient iron, hemoglobin production decreases, leading to fatigue, weakness, and other symptoms associated with anemia. While several factors can contribute to this condition, the root cause always relates to a negative iron balance in the body, which can be broken down into three main categories: blood loss, impaired absorption, and inadequate dietary intake.

Gastrointestinal (GI) Bleeding and Other Blood Loss

Chronic blood loss is the most common cause of IDA in men and postmenopausal women. This often involves slow, unnoticed bleeding. Common causes of GI blood loss include conditions like peptic ulcers, colon polyps, and colorectal cancer. NSAID use can also induce stomach bleeding. Heavy or prolonged menstrual bleeding (menorrhagia) is the most frequent cause in premenopausal women. Other sources include frequent blood donation and bleeding from kidney or bladder issues.

Impaired Iron Absorption

Conditions or surgeries can prevent the body from effectively absorbing iron. Celiac disease and inflammatory bowel disease damage the gut lining, hindering absorption. Gastric surgeries can also reduce absorption. Some medications like antacids can interfere with iron absorption.

Insufficient Dietary Iron Intake

A diet low in iron is a significant cause of IDA globally. Consistent lack of iron-rich foods can lead to deficiency. Vegetarians and vegans are at higher risk as non-heme iron is less efficiently absorbed. Infants and children during growth have high iron needs; prolonged breastfeeding without solids or high cow's milk consumption can cause IDA.

Blood Loss vs. Dietary Factors: A Comparison Table


Feature	Blood Loss	Dietary Factors	Impaired Absorption
Mechanism	The body loses iron-rich red blood cells faster than they can be replaced.	The body's intake of iron is insufficient to meet its daily needs.	The body cannot effectively absorb iron from the digestive tract.
Common in Adults	Men, postmenopausal women, and women with heavy periods.	Less common in developed countries; more prevalent globally.	Individuals with gastrointestinal disease or past surgery.
Key Conditions	Gastrointestinal ulcers, cancers, inflammatory bowel disease, heavy menstrual bleeding.	Vegetarian/vegan diets, lack of access to iron-rich foods, restrictive eating habits.	Celiac disease, Crohn's disease, gastric bypass surgery, certain medications.
Symptom Onset	Often gradual, as chronic loss slowly depletes reserves.	Often gradual, as reserves are used up over time.	Can be insidious, with symptoms developing slowly despite a normal diet.
Diagnosis Clue	Occult blood in stool, heavy menstruation history.	Dietary history review.	Presence of digestive disorders, previous surgeries.

Increased Iron Requirements

Periods of increased demand, like pregnancy, infancy, and adolescence, heighten the risk of IDA if iron intake isn't sufficient. Pregnancy requires significant iron for increased blood volume and fetal development. Rapid growth also raises iron needs.

Conclusion

The main cause of IDA is a negative iron balance. In adults in developed nations, blood loss, particularly chronic GI bleeding in men and postmenopausal women, is the most significant factor. For premenopausal women, heavy menstruation is the most common cause. Other key drivers include insufficient dietary iron intake and impaired absorption. Life stages with increased demand, such as pregnancy, also contribute. Identifying the specific underlying cause is crucial for effective treatment.

For further reading on the diagnosis and management of iron deficiency anemia in adults, refer to the {Link: British Society of Gastroenterology guidelines https://www.bsg.org.uk/resource/british-society-of-gastroenterology-guidelines-for-the-management-of-iron-deficiency-anaemia-in-adults.html}.

Frequently Asked Questions

IDA stands for iron deficiency anemia, a condition where the body does not have enough healthy red blood cells due to a lack of iron. Iron is an essential mineral for producing hemoglobin, which carries oxygen in the blood.

IDA is typically diagnosed through a complete medical history, physical exam, and blood tests. Tests check hemoglobin levels, serum ferritin (iron stores), and transferrin saturation.

While less common in developed countries due to iron-fortified foods, a diet low in iron can cause IDA. Vegetarians and vegans are particularly at risk because plant-based iron is less easily absorbed.

In men and postmenopausal women, chronic gastrointestinal bleeding is the most common cause of IDA because other sources of regular blood loss, like menstruation, are absent. This blood loss can be from conditions such as peptic ulcers, polyps, or cancers.

Symptoms of IDA can include fatigue, weakness, pale skin, shortness of breath, a fast heartbeat, and headaches. Some people might experience unusual cravings for non-food items like ice or dirt (pica).

Yes, pregnancy significantly increases the risk of IDA. The body requires a much larger amount of iron to support the increased blood volume and provide for the developing fetus, which can quickly deplete a pregnant person's iron stores if not supplemented.

Treatment for IDA involves addressing the underlying cause and replenishing iron stores. This is typically done with oral iron supplements, though intravenous iron infusions may be necessary in cases of poor absorption, intolerance, or severe anemia.