What can cause an iron deficiency?

January 10, 2026 •

4 min read

According to the World Health Organization, iron deficiency is the most common nutritional disorder globally, affecting roughly one-third of the world's population. This widespread condition arises from a variety of factors that can cause an iron deficiency, impacting people of all ages and demographics.

Quick Summary

Iron deficiency stems from several key factors, including inadequate dietary intake, various forms of blood loss, impaired iron absorption due to certain medical conditions, and an increased bodily demand for the mineral during different life stages, like pregnancy or growth spurts.

Key Points

Blood Loss: In adults, chronic or acute blood loss, especially from menstruation or the gastrointestinal tract, is the most common cause of iron deficiency.
Malabsorption: Conditions like celiac disease, inflammatory bowel disease, and stomach surgery can impair the body's ability to absorb iron, regardless of dietary intake.
Dietary Factors: Inadequate intake of iron-rich foods or consuming substances like coffee and tea that inhibit absorption can lead to a deficiency.
Increased Demands: Life stages such as pregnancy, rapid growth in children and adolescents, and high-intensity exercise significantly increase the body's iron requirements.
Chronic Illness: Long-term conditions like chronic kidney disease and inflammatory disorders can disrupt iron metabolism and contribute to deficiency.
Hidden Bleeding: In men and postmenopausal women, unexplained iron deficiency often points toward occult internal bleeding that requires investigation.

Iron is a vital mineral that plays a crucial role in the body, primarily as a component of hemoglobin, which carries oxygen in the blood. A deficiency can lead to fatigue, shortness of breath, and other health issues. While a poor diet is a common culprit, many other physiological and pathological reasons can deplete the body's iron stores.

Blood Loss: The Most Common Culprit

For adults, particularly in developed countries, blood loss is the primary cause of iron deficiency. The body recycles iron from old red blood cells, but this process is interrupted when blood is lost from the body. Chronic, low-level bleeding is especially dangerous as it may go unnoticed for a long time, slowly depleting iron stores.

Menstruation and Childbirth

Heavy or prolonged menstrual bleeding (menorrhagia) is a significant and common cause of iron deficiency in premenopausal women. The amount of iron lost can overwhelm the body's ability to absorb enough from the diet. Likewise, the blood loss that occurs during childbirth, and the increased iron demand throughout pregnancy, places women at high risk.

Gastrointestinal (GI) Bleeding

In men and postmenopausal women, the most common source of blood loss is from the gastrointestinal tract. This can be caused by several conditions:

Peptic ulcers: Open sores in the lining of the stomach or small intestine can bleed slowly over time.
Medications: The long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen can cause internal bleeding.
GI cancers: Tumors in the stomach or bowel can cause chronic bleeding.
Inflammatory bowel disease (IBD): Conditions like Crohn's disease and ulcerative colitis cause inflammation and can lead to bleeding.

Other Forms of Blood Loss

Less common causes include frequent blood donation, regular nosebleeds, and blood loss from trauma or surgery. Some athletes, particularly long-distance runners, can experience exercise-induced GI bleeding or hemolysis, where red blood cells are destroyed from the impact.

Dietary Factors and Poor Absorption

Even with sufficient dietary intake, certain conditions can prevent the body from absorbing iron properly from food.

Inadequate Iron Intake

For many people, not eating enough iron-rich foods is the main issue. While iron is added to many foods in Western diets, certain dietary patterns can still lead to low intake. Vegetarians and vegans, for example, primarily consume non-heme iron from plant sources, which is less easily absorbed by the body than heme iron from animal products. Similarly, infants and children who consume excessive cow's milk may become deficient, as it is a poor source of iron.

Malabsorption Syndromes

The majority of iron absorption occurs in the small intestine. Problems with this organ can significantly reduce the amount of iron the body can utilize. Common malabsorption conditions include:

Celiac disease: An autoimmune disorder where consuming gluten damages the small intestine lining, impairing nutrient absorption.
Gastric bypass surgery: The surgical procedure alters the path of digestion, bypassing the part of the small intestine where most iron is absorbed.
Atrophic gastritis: An inflammation of the stomach lining that reduces stomach acid, which is necessary to convert iron to an absorbable state.

Increased Iron Requirements

During certain life stages or medical conditions, the body's need for iron increases dramatically, potentially outstripping supply.

Pregnancy and Infancy

Pregnant women require significantly more iron to support their increased blood volume and the developing fetus. If this need is not met, a deficiency can occur. Similarly, premature infants or those with low birth weight may have lower iron stores from birth, and children during growth spurts have higher demands.

Endurance Athletes

Athletes, especially endurance runners, have an increased risk of iron deficiency due to several factors. These include iron loss through sweat, exercise-induced inflammation that affects absorption, and increased red blood cell production.

Chronic Diseases and Other Causes

Long-term health problems can also interfere with iron metabolism.

Chronic Kidney Disease (CKD): Patients with CKD often develop anemia due to reduced production of erythropoietin, a hormone that stimulates red blood cell production.
Inflammation: Chronic inflammatory conditions, such as rheumatoid arthritis or heart failure, can interfere with iron regulation by increasing hepcidin, a hormone that blocks iron absorption.


Cause	Description	At-Risk Groups
Chronic Blood Loss	Sustained internal or external blood loss, often unnoticed.	Premenopausal women, frequent blood donors, individuals with GI diseases.
Inadequate Diet	Consuming insufficient iron-rich foods or a diet with inhibitors.	Vegetarians, vegans, toddlers drinking excessive cow's milk.
Malabsorption	Medical conditions or surgeries that impair nutrient absorption.	Celiac disease, Crohn's disease, gastric bypass patients.
Increased Needs	Higher physiological demand for iron at certain life stages.	Pregnant women, infants, growing adolescents, endurance athletes.
Chronic Diseases	Long-term illnesses that affect iron metabolism or production.	Patients with CKD, inflammatory bowel diseases, or cancer.

Conclusion

While a low-iron diet is a well-known risk, understanding the full spectrum of reasons what can cause an iron deficiency is critical for effective diagnosis and treatment. From significant blood loss and malabsorption disorders to life stage demands and chronic illnesses, the causes are varied. If you suspect an iron deficiency, it is vital to consult with a healthcare professional for a proper diagnosis and to address the underlying issue. Simply taking an iron supplement may not be sufficient, and without identifying the root cause, the deficiency could reoccur or mask a more serious medical condition. Seeking professional medical advice is always the best course of action.

Frequently Asked Questions

Yes, an inadequate dietary intake of iron is a significant cause of deficiency, especially for individuals following a vegetarian or vegan diet who rely on less-absorbable non-heme iron. However, it is not the only cause, and many other factors can play a role.

Several medical conditions can impair iron absorption, including celiac disease, inflammatory bowel disease (Crohn's, ulcerative colitis), and atrophic gastritis. Additionally, gastric bypass and other surgeries on the stomach or intestines can affect absorption.

Heavy menstrual periods (menorrhagia) cause chronic blood loss that can deplete the body's iron stores faster than they can be replenished through diet alone. This is a common cause of iron deficiency in premenopausal women.

Yes, pregnant women are at an increased risk because their bodies need significantly more iron to support both their increased blood volume and the growth and development of the fetus. Iron supplementation is often necessary.

Hidden, or occult, blood loss can occur from internal bleeding caused by peptic ulcers, polyps, gastrointestinal cancers, or the long-term use of NSAIDs. This type of bleeding is often not visible and requires a medical workup to identify.

Chronic conditions like kidney disease, heart failure, and inflammatory disorders can lead to iron deficiency. These illnesses can interfere with the body's regulation of iron and hinder its proper utilization.

Yes, frequent blood donation can lower the body's iron stores and increase the risk of deficiency. Donors are advised to consume more iron-rich foods to help replenish their levels.