What Can Cause Low Iron Levels? A Comprehensive Guide

October 23, 2025 •

4 min read

According to the World Health Organization, iron deficiency is the most prevalent single nutrient deficiency worldwide, affecting approximately one-third of the global population. Learning what can cause low iron levels is the first step toward prevention and treatment, as this condition can lead to fatigue, weakness, and other significant health issues.

Quick Summary

Low iron levels result from blood loss, inadequate dietary intake, or impaired absorption due to various health conditions. High-risk groups include women with heavy periods, pregnant individuals, and those with specific gastrointestinal disorders. Identifying the underlying cause is crucial for effective treatment and avoiding serious health complications.

Key Points

Blood Loss: The most frequent cause of low iron in adults, often due to heavy menstrual cycles in women or gastrointestinal bleeding.
Dietary Factors: Vegetarian and vegan diets, as well as unbalanced eating habits, can contribute to low iron intake, particularly if not properly planned.
Absorption Issues: Conditions like Celiac disease, Inflammatory Bowel Disease (IBD), and certain surgeries can prevent the body from absorbing iron from food.
Increased Needs: Life stages such as pregnancy, breastfeeding, and rapid growth spurts in children significantly increase the body's demand for iron.
Underlying Conditions: Chronic inflammatory diseases, kidney disease, and autoimmune disorders can all disrupt the body's iron regulation and usage.
Identifying the Cause: Simple iron supplementation may not be enough; a healthcare provider must identify and address the root cause for effective and lasting treatment.

What Causes Low Iron Levels: Understanding the Core Reasons

Iron is an essential mineral vital for producing hemoglobin, a protein in red blood cells that carries oxygen throughout the body. When the body's iron stores are too low, it can lead to iron deficiency and, if severe, iron deficiency anemia. The causes are varied and can stem from dietary, physiological, and pathological factors.

Chronic Blood Loss

This is the most common cause of low iron levels in adults, particularly in men and postmenopausal women, and is a significant factor for premenopausal women as well.

Heavy Menstrual Periods: Women with heavy or prolonged menstrual bleeding, a condition known as menorrhagia, are at a high risk of developing iron deficiency.
Gastrointestinal (GI) Bleeding: Internal bleeding from the GI tract can be a slow, chronic source of blood loss that often goes unnoticed. Common culprits include:
- Stomach Ulcers: Sores in the stomach lining that can bleed slowly.
- GI Cancers: Cancers in the stomach or colon are a serious, though less common, cause.
- NSAID Use: The regular, long-term use of non-steroidal anti-inflammatory drugs like ibuprofen and aspirin can cause GI bleeding.
Frequent Blood Donation: Regular blood donors lose a significant amount of iron with each donation and need to replenish their stores.

Inadequate Dietary Iron Intake

While less common in developed countries due to fortified foods, a diet lacking sufficient iron can cause low levels, especially in specific populations.

Vegetarian and Vegan Diets: Plant-based diets contain non-heme iron, which is less easily absorbed by the body than heme iron found in meat. A well-planned diet with sufficient plant-based iron sources is necessary to compensate.
Poor Overall Diet: Fad dieting, restrictive eating habits, and consuming large amounts of certain foods that inhibit iron absorption can lead to deficiency.
Infants and Toddlers: During rapid growth phases, children require more iron. Giving infants cow's milk too early or exclusively breastfeeding beyond six months without introducing iron-rich solids can lead to low iron levels.

Impaired Iron Absorption

Even with adequate dietary intake, the body may fail to absorb iron properly due to various medical conditions or surgeries.

Celiac Disease: This autoimmune disorder damages the lining of the small intestine, where iron absorption primarily occurs.
Gastric Bypass Surgery: Operations that bypass or remove part of the stomach or small intestine can significantly reduce iron absorption.
Inflammatory Bowel Diseases (IBD): Conditions like Crohn's disease and ulcerative colitis cause chronic inflammation of the digestive tract, impairing nutrient absorption.
Certain Medications: Antacids and other medications that reduce stomach acid can hinder the body's ability to absorb iron, which requires an acidic environment.

Increased Iron Requirements

Some life stages and activities demand a higher iron intake than usual, increasing the risk of deficiency.

Pregnancy and Breastfeeding: The body's blood volume and the developing fetus's needs increase iron requirements during pregnancy. Breastfeeding women also have elevated iron needs.
Growth Spurts: Adolescence is another period of rapid growth that can deplete iron stores if the diet doesn't keep up with the increased demand.
Strenuous Exercise: Athletes, especially endurance athletes, have a higher iron turnover due to increased red blood cell production and iron loss through sweat.

Comparison of Major Causes of Low Iron Levels


Cause	Mechanism	At-Risk Population	Key Indicator	Treatment Approach
Chronic Blood Loss	Ongoing loss of iron-rich blood from the body, often from internal sources.	Premenopausal women (heavy periods), men and postmenopausal women (GI bleed).	Normal diet, but low ferritin and hemoglobin.	Treat underlying bleeding source, iron supplements.
Poor Dietary Intake	Insufficient consumption of iron-rich foods, especially meat.	Vegetarians, vegans, dieters, and those with limited access to nutrient-rich food.	Low ferritin, possible poor dietary history.	Dietary changes, oral iron supplementation.
Impaired Absorption	Inability to absorb iron from food effectively due to GI issues.	Celiac disease patients, post-bariatric surgery patients, IBD patients.	Normal or high iron diet, but low ferritin. GI symptoms may be present.	Treat underlying condition, parenteral iron may be needed.
Increased Needs	Higher physiological demand for iron that exceeds intake.	Pregnant women, adolescents during growth spurts, endurance athletes.	Low ferritin despite adequate diet, specific life stage.	Increased dietary intake, supplements during high-need periods.

Conclusion: Addressing the Root Cause is Key

Identifying the underlying cause is the most critical step for anyone experiencing low iron levels. While many cases can be effectively managed with dietary adjustments or oral iron supplements, these treatments won't address the core problem if it's a result of chronic blood loss or malabsorption. For example, supplementing with iron will only provide a temporary fix if an underlying stomach ulcer continues to bleed. A healthcare professional can help diagnose the specific reason through blood tests and potentially further investigations to ensure the correct course of action. Addressing the root cause not only resolves the iron deficiency but also prevents potential complications from the underlying condition.

For more detailed information on treating iron deficiency anemia, including different iron formulas and monitoring protocols, consult the comprehensive guide at the National Institutes of Health.

Frequently Asked Questions

Yes, a diet low in iron is a possible cause, but in adults, it is rarely the only cause unless you are pregnant, following a strict vegetarian or vegan diet, or have a poor overall diet. In many cases, it's a contributing factor alongside other issues like blood loss or malabsorption.

Heavy or prolonged menstrual bleeding (menorrhagia) is a very common cause of iron deficiency in premenopausal women because it leads to a chronic loss of iron-rich blood from the body.

Conditions that affect the small intestine, where iron is absorbed, can cause malabsorption. These include Celiac disease, Crohn's disease, and surgical procedures like gastric bypass.

It is very common to develop iron deficiency during pregnancy because the body needs extra iron to support the increased blood volume and the growth of the baby. Supplements are often necessary to meet this increased demand.

Yes, long-term use of certain medications, such as non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen, can cause chronic bleeding in the stomach. Antacids can also interfere with iron absorption.

Endurance athletes have an increased need for iron due to higher rates of red blood cell production. They also lose iron through sweating and the breakdown of red blood cells during strenuous exercise, leading to a higher risk of deficiency.

Iron deficiency occurs when the body's iron stores are low, but hemoglobin levels are still normal. Iron deficiency anemia is a more severe stage where the lack of iron is significant enough to reduce hemoglobin production, causing symptoms like fatigue and paleness.