An essential mineral the body uses to carry oxygen in the blood, produce energy, and build many enzymes. Iron deficiency is the most common nutritional deficiency in the world — and at the same time, iron supplementation is one of the most misused. The right dose for one person can be too much for another.

Role in the body Hemoglobin and myoglobin oxygen transport; cofactor for cytochromes in energy production; required for many enzyme systems

Recommended daily intake

Adult Men · 8 mg
Adult Women 19 50 · 18 mg
Adult Women 51 Plus · 8 mg
Pregnancy · 27 mg
Lactation · 9-10 mg

Upper intake limit

45 mg/day for adults (lower in children)

Signs of deficiency

Fatigue, weakness, shortness of breath with exertion
Pale skin, brittle nails, hair loss
Cold hands and feet
Restless legs at night
Pica — cravings for ice, dirt, or starch
Low ferritin and low hemoglobin on bloodwork

Essential building block of hemoglobin, the protein that carries oxygen from lungs to tissues
Required for energy production at the cellular level
Required for normal cognitive development in children
Heme iron from animal foods is absorbed more efficiently than non-heme iron from plant foods
Vitamin C dramatically improves absorption of non-heme iron — pair iron-rich plant foods with citrus or peppers
Premenopausal people, growing children, and pregnant people have higher needs and more risk of deficiency

Active in Fe²⁺ (ferrous), Fe³⁺ (ferric).

Do not supplement iron without confirming deficiency through bloodwork — excess iron is genuinely harmful

Iron overload causes oxidative damage to liver, heart, and pancreas over time

Hemochromatosis (an inherited iron-overload condition) affects roughly 1 in 200 people of Northern European descent — they should never supplement

Iron pills are the leading cause of pediatric poisoning deaths in some countries — keep locked away from children

Reduces absorption of fluoroquinolone and tetracycline antibiotics, levothyroxine, and many other medications — separate doses by at least 2 hours

Calcium, coffee, tea, and dairy reduce iron absorption — take supplements between meals if tolerated

Common side effects include constipation, nausea, and dark stools — taking with food and switching forms (gentler iron bisglycinate) often helps

NIH ODS — Iron · MedlinePlus — Iron · Britannica — Iron

Use with caution

Calcium Calcium competes with non-heme iron for the DMT1 transporter; co-administration reduces iron absorption by 30–60%. Take at separate meals.

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