Iron Dosage Guide (2026): How Much Iron Per Day by Age & Sex
Summarizes NIH guidance and published clinical research — not medical advice. Iron supplementation should be guided by a blood test and a clinician.
Quick answer
Most adults need 8–18 mg of iron per day from food: 8 mg for men and post-menopausal women, 18 mg for menstruating women, and 27 mg in pregnancy. Most people meet this through diet and don't need a supplement. When a blood test shows you're low, the modern approach is roughly 60–100 mg of elemental iron every other day — which absorbs better and is gentler than daily dosing — taken with vitamin C.
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How much iron do you need?
Your daily requirement depends on age, sex, and life stage. This shows your RDA and whether you're in a higher-need group worth a ferritin test — it doesn't diagnose deficiency.
Recommended Daily Allowance (RDA)
These are the total daily iron needs from all sources (food + supplements), set by the National Institutes of Health:
| Age Group | Male | Female | Pregnant | Lactating |
|---|---|---|---|---|
| 1-3 years | 7 mg | 7 mg | — | — |
| 4-8 years | 10 mg | 10 mg | — | — |
| 9-13 years | 8 mg | 8 mg | — | — |
| 14-18 years | 11 mg | 15 mg | 27 mg | 10 mg |
| 19-50 years | 8 mg | 18 mg | 27 mg | 9 mg |
| 51+ years | 8 mg | 8 mg | — | — |
Source: NIH Office of Dietary Supplements. Vegetarians and vegans are advised to aim ~1.8× higher, because non-heme (plant) iron is absorbed less efficiently. The Tolerable Upper Intake Level is 45mg/day for adults.
Elemental iron vs. tablet strength
This trips up almost everyone. An iron tablet is only partly iron — the rest is the salt it's bound to. "Elemental iron" is the amount your body actually gets, and it's the number that matters for dosing. A "325mg" ferrous sulfate tablet is really about 65mg of elemental iron.
| Form | % Elemental Iron | Elemental iron in a 325 mg tablet |
|---|---|---|
| Ferrous fumarate | ~33% | ~106 mg |
| Ferrous sulfate | ~20% | ~65 mg |
| Ferrous gluconate | ~12% | ~38 mg |
| Ferrous bisglycinate ("gentle iron") | labeled as elemental | usually 25–36 mg per capsule |
How to read the label: look at the Supplement Facts panel for the "Iron" line and its milligram amount — that's the elemental iron. Bisglycinate products typically state the elemental amount directly (e.g., 25mg), which is one reason they're easy to dose.
The modern approach: alternate-day dosing
If you're treating a confirmed deficiency, the old advice — a large dose two or three times a day — turns out to be partly self-defeating. A big iron dose spikes hepcidin, the hormone that shuts down iron absorption for roughly a day, so dosing more often doesn't proportionally help and just adds side effects. Research found that a single dose every other day raised the fraction absorbed and reduced GI upset (Stoffel 2017, PMID: 29032957; Kamath 2024, PMID: 37979057). The AGA's clinical update on iron deficiency reflects this shift toward lower-frequency dosing (DeLoughery 2024, PMID: 38864796). Practically, many people do well on ~60–100mg of elemental iron every other day with vitamin C — but let your doctor set the target based on how depleted you are. See iron for anemia & low ferritin for the full treatment picture.
How to absorb iron better
- Pair it with vitamin C. Take iron with a citrus fruit, a glass of orange juice, or a vitamin C supplement — it meaningfully increases absorption of non-heme iron.
- Empty-ish stomach, if you tolerate it. Food lowers absorption, but if iron upsets your stomach, taking it with a little food is a fair trade for staying consistent.
- Separate from blockers. Keep iron a couple of hours away from calcium supplements, dairy, coffee, and tea — all blunt absorption.
- Choose a tolerable form. You'll be taking it for months, so tolerability wins. Ferrous bisglycinate causes less constipation and nausea than ferrous sulfate. See ferrous sulfate vs bisglycinate.
- Be patient. Hemoglobin recovers in weeks, but ferritin — your storage tank — takes 3–6 months to refill. Recheck ferritin, not just hemoglobin, before stopping.
When you should not take iron
Iron is genuinely one to be careful with. Skip supplemental iron unless a test says otherwise if:
- You have no confirmed deficiency — a normal or high ferritin means you don't need it, and extra iron isn't a wellness booster.
- You have hemochromatosis or another iron-overload condition.
- You've had unexplained iron deficiency without finding the cause — deficiency in men and post-menopausal women especially can signal bleeding that needs investigation first.
The safe rule: a ferritin test is cheap, iron overload is not reversible on your own, and "just in case" iron does more harm than good.
If you're supplementing: gentle iron picks
For a confirmed deficiency, tolerability is what keeps you on iron long enough to refill your stores, so these are all well-tolerated bisglycinate ("gentle iron"), ranked by cost per day:
Gentle bisglycinate at 25 mg elemental — well tolerated for long courses.
Lowest cost per day; 36 mg Ferrochel bisglycinate.
NSF Certified for Sport bisglycinate — for tested athletes.
Compare every verified pick on the best iron ranking, or read iron for women and iron for anemia & low ferritin.
Frequently asked questions
How much iron should I take per day?
The RDA is 8mg for men and post-menopausal women, 18mg for menstruating women (19-50), and 27mg in pregnancy — from all sources. Most people meet this from food. Treating a confirmed deficiency is different and higher (~60-100mg elemental iron, ideally every other day).
How much iron should a woman take?
18mg/day for women 19-50 who menstruate, 27mg in pregnancy, and 8mg after menopause — total from food and supplements. A supplement is only needed if a blood test shows low ferritin.
Should I take iron without a blood test?
No. Your body can't excrete excess iron, so taking it when you're not deficient risks GI upset and overload. Test ferritin first and supplement only if you're low, ideally with a clinician.
What's the best way to absorb iron?
Take it with vitamin C, on a relatively empty stomach, and away from calcium, dairy, coffee, and tea. Ferrous bisglycinate is better tolerated than ferrous sulfate.
Elemental iron vs tablet strength?
Iron salts are only partly iron: a 325mg ferrous sulfate tablet is ~65mg elemental iron. Elemental iron is the number that matters — check the Supplement Facts panel.
Related guides
- Iron for Anemia & Low Ferritin — dose, duration, and absorption for a confirmed deficiency
- Ferrous Sulfate vs Bisglycinate — the tolerability difference that matters over months
- Iron for Women — menstruation, pregnancy, and higher needs
- Best Iron Supplements — products ranked by cost per dose
- All Iron Products
Sources
- NIH Office of Dietary Supplements. "Iron: Fact Sheet for Health Professionals." ods.od.nih.gov
- Stoffel NU, et al. "Iron absorption from oral iron supplements given on consecutive versus alternate days." Lancet Haematol. 2017;4(11):e524-e533. PMID: 29032957
- Kamath, et al. "Alternate-day versus daily oral iron for treatment of iron deficiency." 2024. PMID: 37979057
- DeLoughery TG, et al. "AGA Clinical Practice Update on Management of Iron Deficiency Anemia." 2024. PMID: 38864796