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How much iron do I need per day? RDA by sex and life stage

Adult man: 8 mg/day · Women 19–50: 18 mg/day · Pregnancy: 27 mg/day (IOM/NIH). Enter your daily dietary iron to see if you meet your RDA. Free iron intake calculator.

🗓️ Updated June 2026 Reviewed by Martín Rodríguez

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Reviewed by: Martín Rodríguez (editorial policy ) · Last reviewed: Jun 20, 2026

Sex and life stage*

Iron consumed from diet (mg/day)*

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Iron is essential for making hemoglobin, the protein in red blood cells that carries oxygen throughout the body. The Recommended Dietary Allowance (RDA) varies significantly by sex and life stage: adult men and postmenopausal women need just 8 mg/day; women of reproductive age need 18 mg/day due to menstrual blood loss; and pregnant women need 27 mg/day to support the 50% increase in blood volume and build fetal iron stores. Select your group, enter your estimated daily dietary iron intake, and see whether you are meeting, falling short of, or exceeding your RDA.

When to use this calculator

A woman with heavy periods who suspects iron deficiency and wants to know how many mg per day she is falling short.
A pregnant woman checking whether her diet covers the 27 mg/day RDA or whether she needs a prescribed supplement.
A man experiencing chronic fatigue or an athlete wanting to verify his dietary iron intake is within the recommended range.
Someone switching to a vegetarian diet who needs to recalculate their iron target (the IOM recommends multiplying RDA × 1.8 for non-heme iron).

Daily Iron RDA by Sex and Life Stage (IOM/NIH)

Group	RDA (mg/day)	Vegetarian adjustment (×1.8)
Adolescent male 14–18	11	~20 mg/day
Adolescent female 14–18	15	~27 mg/day
Men 19–50	8	~14 mg/day
Men over 50	8	~14 mg/day
Women 19–50	18	~32 mg/day
Women over 50 (postmenopause)	8	~14 mg/day
Pregnancy (any age)	27	~49 mg/day
Breastfeeding 19+	9	~16 mg/day
Tolerable Upper Level (UL) — adults	45	—

Fuente: IOM Dietary Reference Intakes (2001) y NIH Office of Dietary Supplements — Iron Fact Sheet for Health Professionals (ods.od.nih.gov).

How it works

Daily iron RDA by group — reference table (IOM/NIH)

Group	mg/day
Men 19–50	8
Men over 50	8
Women 19–50	18
Women over 50 (postmenopause)	8
Pregnancy (any age)	27
Breastfeeding 19+	9
Adolescent male (14–18)	11
Adolescent female (14–18)	15

Vegetarians: The IOM recommends multiplying the RDA × 1.8 for vegetarians and vegans. A vegetarian adult man should aim for ~14 mg/day; a vegetarian adult woman (19–50) should aim for ~32 mg/day.

Why iron matters

Iron is the core component of hemoglobin (red blood cells) and myoglobin (muscles). Without adequate iron, oxygen-carrying capacity drops, causing fatigue, pallor, hair loss, brittle nails, and reduced cognitive performance — known as iron-deficiency anemia, the most prevalent nutritional deficiency worldwide according to the WHO.

How it is calculated

Coverage (%) = daily_intake_mg / group_RDA × 100
Deficit (mg)  = group_RDA − daily_intake_mg

Intake between 90% and 120% of the RDA is considered adequate. Below 90% indicates a deficit; above 120% warrants monitoring to stay well under the tolerable upper level (UL = 45 mg/day).

Types of dietary iron and absorption

Type	Sources	Average absorption
Heme iron	Red meat, liver, poultry, fish	15–35%
Non-heme iron	Legumes, spinach, tofu, nuts	2–20%

Consuming vitamin C alongside non-heme iron sources can boost absorption by up to 300%. Tea, coffee, and dairy significantly reduce it.

Iron-rich foods — reference table (mg per 100g)

Food	Iron (mg)	Type
Pumpkin seeds	8.8	Non-heme
Cooked mussels	6.7	Heme
Beef liver	6.2	Heme
Cooked spinach	3.6	Non-heme
Cooked lentils	3.3	Non-heme
Beef steak	2.7	Heme
Tofu	2.7	Non-heme
Cooked quinoa	1.5	Non-heme
Whole egg	1.0	Non-heme

Signs of iron deficiency

Persistent fatigue without an obvious cause.

Pale skin and conjunctivae.

Diffuse hair loss.

Brittle nails or spoon-shaped nails (koilonychia).

Difficulty concentrating.

Serum ferritin < 30 ng/mL (most sensitive early marker).

Supplementation

Ferrous sulfate: economical and effective, but may cause constipation and nausea.

Iron bisglycinate (chelated): similarly or better absorbed with far fewer gastrointestinal side effects.

Alternate-day dosing: recent evidence (Moretti 2020, PLOS ONE) suggests every-other-day iron may be more effective by reducing hepcidin suppression.

Tolerable Upper Level (UL): 45 mg/day for adults. Do not exceed without medical guidance.

Editorial note

Reviewed by the Hacé Cuentas editorial team. Reference values are from the IOM DRI (2001), cross-checked against the NIH Office of Dietary Supplements fact sheet.

Disclaimer: Results are informational only and do not replace medical advice. Low ferritin or anemia require professional diagnosis. Do not start or modify iron supplementation without a doctor's recommendation.

Example: Pregnant woman with a mixed diet

Group: Pregnancy → RDA = 27 mg/day (IOM/NIH).

Estimated daily diet: 100g beef sirloin (2.7 mg) + 150g cooked lentils (4.9 mg) + 80g cooked spinach (2.9 mg) + 30g pumpkin seeds (2.6 mg) + rest of meals (~4 mg) = ~17 mg/day.

Calculation: 17 mg received / 27 mg RDA = 63% coverage.

Deficit: 27 − 17 = 10 mg/day — typically covered by a prescribed iron supplement during prenatal care.

A typical mixed diet during pregnancy covers about 63% of the RDA (17 out of 27 mg). The 10 mg/day deficit is usually covered with a doctor-prescribed iron supplement.

Frequently asked questions

How much iron do I need per day as an adult man?

The RDA for adult men (19–50 years) and men over 50 is 8 mg/day. This is the lowest requirement among adults because men do not lose iron through menstruation. Vegetarian men should target around 14 mg/day due to lower non-heme iron absorption.

How much iron does a woman need per day?

Women aged 19–50 need 18 mg/day — more than twice the male requirement — because menstrual blood loss depletes iron stores monthly. After menopause, the female RDA drops to 8 mg/day, matching the male requirement.

Why does pregnancy require so much iron (27 mg/day)?

During pregnancy, blood volume increases by roughly 50%, the uterus and placenta require additional iron, and the fetus builds its own iron stores for the first 6 months after birth. The IOM set the RDA at 27 mg/day because diet alone almost never covers this amount — most pregnant women need a prescribed supplement.

How do I estimate how many mg of iron I eat per day?

Add up the iron content of your usual foods using composition tables or apps like Cronometer or MyFitnessPal. Quick references: 100g cooked lentils ≈ 3.3 mg; 100g beef steak ≈ 2.7 mg; 100g cooked spinach ≈ 3.6 mg; 1 whole egg ≈ 1 mg; 40g fortified cereal ≈ 4–8 mg.

Do vegetarians and vegans need more iron?

Yes. The IOM recommends multiplying the standard RDA by 1.8 for vegetarians and vegans. Non-heme plant iron is absorbed at only 2–20% versus 15–35% for heme iron from meat. A vegetarian adult man should aim for about 14 mg/day; a vegetarian adult woman in her reproductive years should aim for about 32 mg/day.

Does tea, coffee, or calcium block iron absorption?

Yes, significantly. Tannins in black and green tea and chlorogenic acid in coffee can reduce non-heme iron absorption by up to 60%. Calcium (from dairy or supplements) also competes with iron for absorption. Ideally, leave 1–2 hours between your main iron-containing meal and these beverages or calcium supplements.

What are the symptoms of iron deficiency?

The most common signs are persistent fatigue, pale skin, pale inner eyelids, diffuse hair loss, brittle or spoon-shaped nails, shortness of breath on mild exertion, headaches, and difficulty concentrating. A blood test (serum ferritin + complete blood count) is needed to confirm the diagnosis. Low ferritin (< 30 ng/mL) can cause symptoms even before anemia develops.

Can you take too much iron?

Yes. The Tolerable Upper Level (UL) is 45 mg/day for adults. Chronic excess iron causes gastrointestinal distress, and in people with hereditary hemochromatosis it leads to serious organ damage. Never supplement above the RDA without a confirming blood test and a doctor's prescription.

Why is ferritin a better test than hemoglobin for iron status?

Hemoglobin drops only once anemia is fully established — it is the last indicator to fall. Serum ferritin reflects iron stores and drops weeks to months earlier. A ferritin level below 30 ng/mL with normal hemoglobin — called non-anemic iron deficiency — already causes fatigue, hair loss, and reduced cognitive performance. Always request both tests.

How much iron do adolescent girls need?

Adolescent females (14–18 years) need 15 mg/day, higher than adolescent males (11 mg/day), because they have both active growth requirements and menstrual losses. Iron-deficiency anemia is very common in teenage girls and is associated with poor concentration and reduced athletic performance.

Sources & references

Methodology & trust

Editorial

Calculadora de salud revisada por el equipo editorial de Hacé Cuentas, contrastada con NIH Office of Dietary Supplements — Iron Fact Sheet for Health Professionals, según nuestra política editorial y metodología.

Updates

Última revisión: June 20, 2026. Los parámetros se verifican periódicamente con las fuentes citadas.

Privacy

Calculations run 100% in your browser. We do not store or transmit your data.

Limitations

Indicative results. For critical decisions, consult a professional.

📌 How to cite this calculator

Rodríguez, M. (2026). How much iron do I need per day? RDA by sex and life stage. Hacé Cuentas. https://hacecuentas.com/daily-iron-requirements-by-sex-age

Contenido bajo licencia CC-BY 4.0 — reutilizable citando la fuente con enlace a Hacé Cuentas.

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