Iron

Medically reviewed by Prof. Giorgi Pkhakadze, MD, MPH, PhD — GMJ Editorial Board

What is Iron?

Iron is an essential mineral that plays a crucial role in numerous bodily functions, most notably in oxygen transport and energy metabolism. As one of the most abundant elements on Earth, iron is vital for human health, yet iron deficiency remains the most common nutritional deficiency worldwide, affecting approximately 2 billion people globally.

Scientific name: Fe (from Latin: ferrum)
Category: Essential mineral
RDA: 8 mg/day (adult men), 18 mg/day (adult women)
UL: 45 mg/day (adults)

Iron exists in two dietary forms: heme iron (found in animal products) and non-heme iron (found in plant sources and supplements). The body absorbs heme iron more efficiently than non-heme iron, making dietary source selection important for maintaining adequate iron status.

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Health benefits & uses

Preventing and treating iron deficiency anemia (Strong evidence): Iron supplementation effectively treats iron deficiency anemia, the most common form of anemia worldwide. Clinical studies consistently demonstrate that iron supplements restore hemoglobin levels and improve symptoms of fatigue and weakness in deficient individuals.

Supporting cognitive function (Moderate evidence): Research indicates that iron deficiency can impair cognitive performance, particularly in children and adolescents. Iron supplementation in deficient populations has shown improvements in attention, memory, and learning capacity.

Enhancing athletic performance in deficient individuals (Moderate evidence): Athletes with iron deficiency may experience improved endurance and reduced fatigue following iron supplementation, though benefits are primarily seen in those with documented deficiency.

Supporting immune function (Limited evidence): Iron plays a role in immune system function, and severe deficiency can impair immune response. However, the relationship is complex, as both deficiency and excess can negatively affect immunity.

How it works

Iron functions primarily as a component of hemoglobin, the protein in red blood cells responsible for transporting oxygen from the lungs to tissues throughout the body. Additionally, iron is essential for myoglobin production, which stores oxygen in muscle tissues.

Iron also serves as a cofactor for numerous enzymes involved in energy metabolism, DNA synthesis, and cellular respiration. The body tightly regulates iron absorption through the hormone hepcidin, which controls iron uptake from the intestines and iron release from storage sites.

When iron stores are adequate, the body absorbs only 10-15% of dietary iron. However, absorption can increase to 35% or more when iron stores are depleted, demonstrating the body’s sophisticated regulatory mechanisms.

Dosage

Typical supplementation ranges vary based on individual needs and iron status. For prevention of deficiency, doses of 15-30 mg daily are commonly used. For treating iron deficiency anemia, therapeutic doses typically range from 100-200 mg of elemental iron daily, usually divided into 2-3 doses.

The Recommended Dietary Allowance (RDA) varies by age and gender: adult men require 8 mg daily, while women of reproductive age need 18 mg daily due to menstrual losses. Pregnant women require 27 mg daily to support increased blood volume and fetal development.

The Tolerable Upper Intake Level (UL) is set at 45 mg daily for adults to prevent adverse effects from excessive intake. Healthcare provider guidance is essential for determining appropriate dosing, as individual needs vary significantly based on iron status, absorption capacity, and underlying health conditions.

Food sources

Heme iron sources include red meat, poultry, fish, and organ meats, with liver being particularly rich in iron. Non-heme iron sources encompass fortified cereals, legumes (lentils, chickpeas, beans), spinach, tofu, quinoa, and dried fruits like raisins and apricots.

Iron absorption can be enhanced by consuming vitamin C-rich foods (citrus fruits, bell peppers, strawberries) alongside iron sources. Conversely, calcium, tannins in tea and coffee, and phytates in whole grains can inhibit iron absorption when consumed simultaneously.

Safety & side effects

Iron supplements are generally safe when used appropriately, but can cause gastrointestinal side effects including nausea, constipation, diarrhea, and stomach upset. Taking iron with food can reduce these effects, though it may also decrease absorption.

Iron toxicity, while rare with recommended doses, can be serious. Acute iron poisoning is a medical emergency, particularly dangerous for children. Chronic iron overload can lead to organ damage, particularly affecting the liver, heart, and pancreas.

Individuals should avoid iron supplements unless deficiency is documented or risk is high, as excessive iron accumulation cannot be easily reversed through natural elimination processes.

Interactions

Iron can significantly reduce absorption of certain medications, including tetracycline and quinolone antibiotics, levothyroxine, and bisphosphonates. These medications should be taken at least 2 hours apart from iron supplements.

Proton pump inhibitors and H2 receptor antagonists can reduce iron absorption by decreasing stomach acid production. Calcium supplements, zinc, and magnesium can also interfere with iron absorption when taken simultaneously.

Conversely, vitamin C supplements enhance iron absorption and are often recommended alongside iron supplementation.

Who should be cautious

Individuals with hemochromatosis or other iron overload disorders should avoid iron supplements entirely. Those with frequent blood transfusions, chronic kidney disease, or certain genetic conditions affecting iron metabolism require careful monitoring.

People with gastrointestinal conditions such as inflammatory bowel disease should consult healthcare providers before supplementing, as iron can exacerbate inflammation in some cases.

Frequently asked questions

Should I take iron supplements if I feel tired?

Fatigue has many causes beyond iron deficiency. Only take iron supplements after confirming iron deficiency through blood tests, as excess iron can be harmful and fatigue may stem from other treatable conditions.

Why do iron supplements cause stomach upset?

Iron can irritate the gastrointestinal lining, leading to nausea, constipation, or diarrhea. Taking supplements with food, starting with lower doses, or trying different formulations (ferrous sulfate vs. ferrous gluconate) may help reduce symptoms.

Can I take iron with my multivitamin?

While possible, calcium and other minerals in multivitamins can reduce iron absorption. For optimal absorption, take iron supplements separately from other supplements, preferably with vitamin C.

How long does it take to correct iron deficiency?

Hemoglobin levels typically improve within 2-4 weeks of starting supplementation, while full iron store replenishment may take 3-6 months. Regular monitoring through blood tests helps track progress.

Are there different types of iron supplements?

Yes, common forms include ferrous sulfate, ferrous gluconate, and ferrous fumarate. Ferrous sulfate is most commonly prescribed due to its high elemental iron content, while other forms may be better tolerated by some individuals.