Trace mineral

Iron

Hemoglobin (oxygen transport), myoglobin, energy metabolism, immunity, cognition

Essential nutrient

Reference intakes (RDA or AI) are set by the National Academies of Sciences, Engineering, and Medicine. Deficiency thresholds come from clinical and WHO guidance.

At a glance

Women, 19-50

18 mg (8 mg after 50; 27 mg pregnancy)

Men, 19-50

8 mg

Upper limit (adults)

45 mg/day

How common is deficiency?

VERY COMMON - most common nutrient deficiency worldwide (especially in women)

Food sources

Animal sources

HEME iron (best absorbed): beef, lamb, liver, oysters, clams, sardines, turkey dark meat

Plant sources

NON-HEME iron: lentils, chickpeas, tofu, spinach, pumpkin seeds, fortified cereals, quinoa, blackstrap molasses (absorption improves with vitamin C)

Deficiency and testing

Signs of deficiency

Fatigue, pallor, weakness, shortness of breath, dizziness, cold hands/feet, brittle nails, hair loss, restless legs, pica (ice craving), poor concentration

Who is at higher risk

Menstruating and pregnant women, infants/toddlers, vegetarians/vegans, frequent blood donors, GI bleeding, celiac/IBD, bariatric surgery, endurance athletes

How it is tested

Serum ferritin (best stores marker); serum iron; TIBC; transferrin saturation; hemoglobin/hematocrit; MCV; soluble transferrin receptor; reticulocyte Hb

Cut-offs

Ferritin <30 ng/mL = iron deficiency (<15 ng/mL absolute, WHO); transferrin saturation <20%; Hb <13 g/dL men, <12 g/dL women = anemia

Symptoms are not specific. Only a clinician with the right tests can tell whether you are deficient.

Supplement forms

Common forms

ferrous sulfate, ferrous fumarate, ferrous gluconate, iron bisglycinate (chelate), iron polysaccharide complex, carbonyl iron, heme iron polypeptide, liposomal/sucrosomial iron, IV iron (iron sucrose, ferric carboxymaltose).

More effective

ferrous salts (sulfate, fumarate, gluconate) are proven, inexpensive, and absorbed best; alternate-day dosing of 40-80 mg elemental iron improves fractional absorption and cuts side effects; iron bisglycinate is better tolerated with similar or better absorption; take with vitamin C and apart from tea, coffee, dairy, and calcium. IV iron when oral fails, is not tolerated, or absorption is poor (celiac, IBD, bariatric surgery, kidney disease, pregnancy).

Less effective

ferric (Fe3+) salts and slow-release products (lower absorption); iron taken with calcium, tea, coffee, or PPIs; liposomal and sucrosomial iron (promising but less proven); daily high doses (more nausea and constipation, less absorption). Do not supplement iron without a test because excess iron is harmful (hemochromatosis).

Safety, interactions and halal notes

Safety and interactions

Upper limit for adults: 45 mg/day. Going above the upper limit over time can cause harm, so check labels and talk to a clinician before high-dose supplements.

Halal note

The nutrient itself is not a halal question. For supplements, check the delivery form: gelatin (pork or non-halal bovine), capsule shells, glycerin, and alcohol-based carriers need halal certification. Ask for the halal certificate, not just a label claim. This is general guidance, not a certification.

Frequently asked questions

How much Iron do adults need per day?

Women 19-50: 18 mg (8 mg after 50; 27 mg pregnancy). Men 19-50: 8 mg. Upper limit: 45 mg/day. Needs change with age, pregnancy and health conditions.

What are the signs of Iron deficiency?

Fatigue, pallor, weakness, shortness of breath, dizziness, cold hands/feet, brittle nails, hair loss, restless legs, pica (ice craving), poor concentration. These signs are not specific, so only a clinician with the right tests can confirm a deficiency.

What are the best food sources of Iron?

Animal sources: HEME iron (best absorbed): beef, lamb, liver, oysters, clams, sardines, turkey dark meat. Plant sources: NON-HEME iron: lentils, chickpeas, tofu, spinach, pumpkin seeds, fortified cereals, quinoa, blackstrap molasses (absorption improves with vitamin C).

Which form of Iron supplement is best?

Sources

← Back to the full nutrient guide

This page is for education only and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Supplements are not intended to diagnose, treat, cure or prevent any disease. Talk to a qualified clinician before starting a supplement, especially if you are pregnant, breastfeeding, take medicine or have a medical condition. Daily needs are US reference intakes for adults 19-50.