Why do women need more iron than men?

Menstruation. Women of reproductive age lose iron with monthly blood loss, so the RDA is 18mg for women versus 8mg for men. That is why iron deficiency and iron deficiency anemia are far more common in menstruating women, and why iron is one of the few supplements many women genuinely benefit from. Needs rise further in pregnancy (27mg) and can be higher in women with heavy periods or who train hard.

Should all women take an iron supplement?

No — even for women, supplement based on need, not by default. Many women with normal periods and a varied diet get enough iron from food. The right approach is to supplement if you have symptoms (fatigue, hair shedding, breathlessness, restless legs) or risk factors (heavy periods, pregnancy, vegetarian diet, endurance training) and ideally a blood test showing low ferritin. Taking iron you do not need still carries overload risk, so a ferritin check is worth it before committing.

How much iron should a woman take?

For maintaining adequate iron, the RDA is 18mg for women of reproductive age and 27mg during pregnancy. A typical supplement provides 18-25mg of elemental iron, which suits most women correcting a mild shortfall. Treating a diagnosed deficiency uses higher amounts, often given every other day for better absorption and tolerance, under medical guidance. Pregnant women should follow their prenatal care provider, since prenatal vitamins usually already contain iron.

Best Iron for Women (2026): Periods, Pregnancy, and Why Women Need More

Q: Why are female athletes prone to low iron?

Female endurance athletes are a high-risk group for several reasons stacking on top of menstruation: iron is lost through sweat, foot-strike during running can destroy red blood cells (foot-strike hemolysis), and intense exercise raises hepcidin, which temporarily blocks iron absorption. Low iron in athletes shows up as unexplained fatigue and dropping performance. Active women with these symptoms should have ferritin checked, since low iron can impair training even before anemia develops.

By Verified Supplement Data · Updated May 31, 2026 · Methodology · About Us

Women need more than twice the iron men do (18mg vs 8mg RDA; 27mg in pregnancy) because of menstrual blood loss — which is why iron deficiency is most common in women of reproductive age (Tang 2024, PMID: 38042684).

But supplement on need, not by default: if you have heavy periods, are pregnant, train hard, or eat little meat — and ideally a ferritin test confirms low iron. Use a gentle (bisglycinate) form so you can stick with it.

Best value: Solgar Gentle Iron 25mg. With cofactors: MegaFood Blood Builder (folate + B12 + C).

Why iron is genuinely a women's issue

Most "for women" supplement angles are marketing. Iron is the real thing. Menstruation means a monthly iron loss men simply don't have, which is why the RDA is more than double (18mg vs 8mg) and why iron deficiency anemia is overwhelmingly concentrated in women of reproductive age — a pattern significant enough that researchers frame it as a health-equity issue (Tang 2024, PMID: 38042684). If you're a woman with unexplained fatigue, hair shedding, breathlessness on stairs, or restless legs, low iron is one of the first things genuinely worth checking.

Needs by life stage

Iron requirements for women
Situation	Iron RDA / need	Notes
Women 19-50 (menstruating)	18mg/day	More than double the male RDA
Heavy periods (menorrhagia)	Often higher	Common cause of deficiency; worth testing
Pregnancy	27mg/day	Usually covered by prenatal vitamins — follow your provider
Postmenopausal	8mg/day	Same as men; rarely need a supplement — test before taking
Female endurance athletes	Elevated	Sweat + foot-strike hemolysis + exercise hepcidin

The groups most likely to actually need it

Heavy periods: the most common driver of iron deficiency in women. If your periods are heavy, low iron is likely and a ferritin test is worth it.
Pregnancy: demand jumps to 27mg/day, but prenatal vitamins usually include iron — coordinate with your provider rather than double-dosing.
Endurance athletes: runners especially lose iron through sweat and foot-strike hemolysis, and hard training raises hepcidin. Low iron saps performance before anemia even shows.
Vegetarian/vegan women: plant (non-heme) iron is less absorbable, raising the bar.

Notably not on this list: postmenopausal women, who need no more iron than men and should test before taking any.

How to take it

Use a well-tolerated form — ferrous bisglycinate — because the cheaper ferrous sulfate's constipation and nausea are exactly what make women quit before stores refill. Take it with vitamin C, keep it away from calcium, dairy, coffee, and tea, and consider alternate-day dosing, which absorbs better and is gentler (Stoffel 2017, PMID: 29032957). Refilling ferritin takes months — see iron for anemia & low ferritin.

Best iron for women, ranked

Iron supplements ranked by cost per day
Product	Form	Elemental Iron	Servings	Price	Cost/Day	Certification	Buy
NOW Foods Iron 36 mg Double Strength (Ferrochel) Budget Pick	Ferrous bisglycinate	36mg	90	$9.27	$0.10	None	Buy
Solgar Gentle Iron (Iron Bisglycinate) 25 mg Best Value	Ferrous bisglycinate	25mg	90	$9.65	$0.11	None	Buy
Thorne Iron Bisglycinate 25 mg Quality Pick	Ferrous bisglycinate	25mg	60	$16.00	$0.27	NSF Certified for Sport	Buy
MegaFood Blood Builder	Whole-food + cofactors	26mg	90	$28.99	$0.32	NSF Certified	Buy

Frequently asked questions

Why do women need more iron?

Menstrual blood loss — RDA is 18mg for women vs 8mg for men (27mg in pregnancy). That's why iron deficiency is most common in women of reproductive age.

Should all women take iron?

No — supplement on need. Many women with normal periods and a varied diet get enough. Supplement for symptoms or risk factors (heavy periods, pregnancy, vegetarian, endurance training), ideally with a ferritin test.

How much iron for a woman?

RDA 18mg (reproductive age), 27mg (pregnancy). A typical 18-25mg supplement suits mild shortfalls; treating diagnosed deficiency uses more, often alternate-day, under medical guidance. Pregnant women follow their provider.

Why are female athletes prone to low iron?

Sweat loss, foot-strike hemolysis (running), and exercise-raised hepcidin stack on top of menstruation. Low iron saps performance before anemia — active women with fatigue should check ferritin.

Related guides

Best Iron Supplement
Iron for Anemia & Low Ferritin
Ferrous Sulfate vs Bisglycinate
Creatine for Women · Vitamin C (take with iron)

Sources

Tang GH, et al. "Iron deficiency anemia among women: An issue of health equity." Blood Rev. 2024. PMID: 38042684
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
NIH Office of Dietary Supplements. "Iron: Fact Sheet for Health Professionals." ods.od.nih.gov