Daily Iron Intake: How Much Iron Do You Need by Age and Sex?

✍️ By The DRI Calculator Team  |  📅 Published: June 4, 2026  |  🔄 Updated: June 4, 2026  |  ⏱ 9 min read

Your daily iron intake matters more than most people realize — iron deficiency is the most common nutritional deficiency in the world, affecting roughly 1 in 5 women of reproductive age. The official numbers look simple at first: 8 mg per day for men, 18 mg for premenopausal women, 27 mg during pregnancy. But the real story is more interesting. Your body absorbs only a small fraction of the iron you eat. Plant iron absorbs 2–3 times worse than meat iron. Tea, coffee, and calcium block absorption. Vitamin C boosts it. And the average American woman eats only about 12 mg of iron a day — already short of her 18 mg target before absorption is even factored in. This guide walks through exactly how much iron you need, how to actually get it from food, when to test for deficiency, and what to do about it. (New to RDAs and DRIs? Read our plain-English intro first.)

Daily iron intake by age and sex (quick answer)

Here are the official Recommended Dietary Allowance (RDA) values from NASEM, the body that sets nutrient standards for the US and Canada:

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* Adequate Intake (AI) — used for infants 0–6 months. Source: NASEM DRI tables.

Why your body needs iron

Iron does three big jobs in your body. Without enough of it, all three slow down — and that's where the symptoms come from.

1. Oxygen transport. Iron is the core of hemoglobin, the protein in your red blood cells that carries oxygen from your lungs to every other cell. Roughly 70% of your body's iron lives in hemoglobin. Less iron means less oxygen-carrying capacity — which is why low iron makes you feel tired and short of breath.

2. Energy production. Inside your cells, iron is part of the machinery that turns food into usable energy (ATP). When iron is low, your cells can't make energy efficiently, which causes fatigue that no amount of sleep fixes.

3. Brain and immune function. Iron helps make neurotransmitters like dopamine and serotonin. It also supports immune cell production. This is why iron-deficient people often report brain fog, low mood, and getting sick more often.

Your body holds about 1–3 grams of total iron at any time, and loses around 1 mg per day through shed skin cells and gut lining. Women who menstruate lose an additional 1–2 mg per day on average during their period. That's the entire reason for the gap between men's and women's iron RDAs.

Heme vs non-heme iron — the absorption difference

Here's what most articles skip but matters enormously: not all iron is created equal. There are two forms in food, and they absorb at very different rates.

Heme iron (from animals)

Found in red meat, poultry, fish, and seafood. Your gut absorbs 15–35% of heme iron — a remarkably high rate. This is why animal-eaters rarely struggle with iron deficiency.

Non-heme iron (from plants)

Found in lentils, beans, spinach, fortified cereals, tofu, and most plant foods. Your gut absorbs only 2–20% of non-heme iron — often much lower than that without help.

This is exactly why NASEM notes that vegetarians and vegans may need up to 1.8 times the standard iron RDA from food alone. An 18 mg target effectively becomes 33 mg for a vegan woman trying to hit her needs from plants only. That's hard to do without smart food pairing or a supplement.

Iron-rich foods (with iron content per serving)

Here are the most reliable iron sources, with realistic serving sizes. Heme sources at the top, non-heme below:

Heme iron sources (animal-based)

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Non-heme iron sources (plant-based)

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The % RDA column above assumes 100% absorption, which never happens. For a realistic figure, multiply heme iron values by ~0.25 (25% absorbed) and non-heme by ~0.10 (10% absorbed) — those are the actual amounts you'll absorb.

How to maximize iron absorption (and what blocks it)

You can roughly double the iron your body absorbs just by changing what you eat or drink alongside it. This is one of the most underrated tips in nutrition.

What boosts absorption

• Vitamin C: The single biggest absorption booster. Squeeze lemon juice on lentils, eat strawberries with iron-fortified cereal, drink orange juice with a spinach salad — vitamin C can quadruple non-heme iron absorption.
• Animal protein: A small amount of meat in a meal helps your body absorb the plant iron in the same meal. Even a few ounces of chicken with your beans improves iron uptake.
• Cooking in cast iron: Acidic foods like tomato sauce cooked in a cast-iron pan pick up small amounts of iron from the pan. Not a huge effect, but it adds up.

What blocks absorption

• Tea and coffee: The tannins in tea and polyphenols in coffee can reduce iron absorption by 50–70% when consumed with a meal. Wait an hour before or after iron-rich foods.
• Calcium: A cup of milk or a calcium supplement taken alongside iron blocks absorption. Don't take iron and calcium supplements at the same time.
• Phytates (in whole grains, legumes, nuts): Natural compounds that bind iron. Soaking, fermenting, and sprouting reduce phytates.
• Oxalates (in spinach, beets, chocolate): Reduce absorption of the iron in those same foods. This is why spinach, despite its reputation, is a less efficient iron source than it looks on paper.

Signs of iron deficiency and how to test for it

Iron deficiency develops slowly. Early on, you might just feel a bit more tired than usual. Many women brush off the early signs as poor sleep or a busy week — and that's exactly why deficiency often goes undetected for months.

Early signs (iron stores depleting)

• Persistent tiredness, even with adequate sleep
• Brain fog or trouble concentrating
• Cold hands and feet
• Hair shedding more than usual
• Brittle, ridged, or spoon-shaped fingernails

Later signs (anemia developing)

• Pale skin, especially inside lower eyelids
• Shortness of breath with light activity
• Fast or pounding heartbeat
• Dizziness, especially standing up
• Restless legs syndrome
• Unusual cravings (ice, dirt, clay — called pica)
• Sore or smooth tongue

How to test (ferritin is the key)

The single most useful blood test is serum ferritin, which measures your iron stores. It's more sensitive than a standard hemoglobin test, which only catches deficiency after it's already become anemia.

General ferritin thresholds:

• < 15 ng/mL: Iron deficient (WHO threshold)
• 15–30 ng/mL: Borderline / depleted stores (many clinicians treat this)
• 30–100 ng/mL: Adequate
• > 100 ng/mL: Plenty, sometimes high — check for inflammation

A complete blood count (CBC) plus ferritin plus a serum iron and total iron binding capacity (TIBC) gives the full picture. If you've been tired for weeks and can't pinpoint why, ask your doctor for these labs — they're inexpensive and easy.

Iron during pregnancy: trimester-by-trimester needs

Pregnancy nearly doubles your iron needs — and unlike most nutrients where the change is gradual, iron demand accelerates through the trimesters. By the last 6–8 weeks of pregnancy, your body needs roughly 10 times the iron it did before conception.

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The reason RDA is 27 mg/day across pregnancy (not just the high-need third trimester) is that your gut absorbs iron more efficiently in pregnancy, and the higher daily intake builds stores for when demand peaks.

Iron deficiency in pregnancy isn't just uncomfortable — it's linked to preterm birth, low birth weight, and impaired neurological development in the baby. This is why ACOG recommends screening for anemia at the first prenatal visit and again at 24–28 weeks.

Iron and women's health: periods, anemia, life stages

Roughly 1 in 5 women have heavy menstrual periods, and these women are at especially high risk for iron deficiency anemia. Here's why iron is such a women-specific nutrition issue at every life stage.

Iron during menstruation

The average period causes about 30–40 mL of blood loss, which equates to roughly 15–20 mg of iron lost across the cycle. For women with heavy periods (more than 80 mL per cycle, or soaking through pads/tampons every hour), iron loss can be 40 mg or more per cycle — well over what daily intake can replace.

Iron after childbirth (postpartum)

Childbirth involves significant blood loss — typically 500–1,000 mL for vaginal delivery and more for cesarean. If you started pregnancy with low iron stores, postpartum anemia is common. Your body needs time to rebuild stores, which is one reason lactation RDA is still 9 mg/day — slightly above pre-pregnancy needs for menstruating women on a per-body basis, accounting for breastfeeding losses.

Iron through perimenopause

The years before menopause often involve erratic, heavier-than-usual periods. Many women are unknowingly building iron deficiency during this phase. If you're in your 40s and feel persistently fatigued, get a ferritin check — don't assume "I just eat a healthy diet, I'm fine."

Iron after menopause

Once periods stop, iron RDA drops to 8 mg/day — the same as men. At this stage, the bigger risk shifts from deficiency to overload. Don't continue taking high-dose iron supplements after menopause unless your doctor specifically recommends them.

Iron supplements — types, dosing, and side effects

Supplements are useful when food alone isn't enough — but they're also where most people get into trouble. Here's what to know.

Common types

• Ferrous sulfate — most common, cheapest, well-absorbed. Most likely to cause GI side effects.
• Ferrous gluconate — gentler on the stomach, lower iron per pill (so more pills needed).
• Ferrous bisglycinate (chelated) — best tolerated, absorbed well, more expensive. A good choice if other forms cause constipation.
• Iron polysaccharide complex — gentler GI profile, often used in pediatric drops.
• Heme iron polypeptide — derived from animal sources, mimics natural heme iron, absorbs well.

How to take them

• Take on an empty stomach if you can tolerate it — best absorption.
• Pair with vitamin C (an orange, a glass of OJ, or a 250 mg vitamin C tablet).
• Avoid taking with milk, calcium supplements, antacids, tea, or coffee — wait at least an hour.
• Every other day may work better than daily. Recent research shows your gut absorbs iron more efficiently with rest days between doses. Many doctors now recommend alternate-day dosing.

Standard doses for treating deficiency

• Prevention (pregnancy): 30 mg elemental iron daily (CDC recommendation)
• Mild deficiency: 30–60 mg daily, recheck in 8–12 weeks
• Treating anemia: 60–120 mg daily under medical guidance
• Severe anemia in pregnancy: sometimes IV iron — only with specialist care

Side effects

The most common complaints are constipation, nausea, dark stools, and stomach discomfort. These are mostly dose-related — if you can't tolerate ferrous sulfate, switch to bisglycinate or try every-other-day dosing before giving up.

Too much iron: the safety ceiling (UL = 45 mg)

Iron is one of the nutrients with a relatively narrow safety margin. The Tolerable Upper Intake Level (UL) for adults is 45 mg per day. Above that, you start risking acute and chronic problems.

Short-term overdose risks

• Severe GI distress, nausea, vomiting
• Iron poisoning in children (under age 6) — even a few high-dose adult supplements can be fatal
• Always store iron supplements out of children's reach

Long-term overload risks

• Hemochromatosis — a genetic condition where your body absorbs too much iron. Affects roughly 1 in 200 people of Northern European descent. Iron supplements can be dangerous for people with this condition.
• Iron overload from years of high supplementation can damage liver, heart, and pancreas.
• Postmenopausal women and men are at higher overload risk because they don't lose iron through menstruation.

Iron for vegans, vegetarians, and athletes

Three groups have higher-than-average iron needs and deserve special attention:

Vegans and vegetarians

NASEM notes that vegetarians may need up to 1.8 times the standard RDA from food alone — so a vegan woman 19–50 effectively targets about 33 mg/day from food. This is hard to hit without smart food pairing or a supplement. Practical tips:

• Pair every iron-rich meal with vitamin C
• Soak/sprout legumes and grains to reduce phytates
• Use cast iron cookware for acidic foods
• Consider a daily multivitamin or low-dose iron supplement (especially women)
• Get ferritin tested annually

Endurance athletes

Distance runners, cyclists, and triathletes lose iron through sweat and a phenomenon called "foot-strike hemolysis" (red blood cells damaged by the impact of running). Female athletes are particularly at risk. Most experts recommend testing ferritin yearly for serious endurance athletes, with target ferritin above 30–40 ng/mL for performance.

Frequent blood donors

Each whole blood donation removes about 200–250 mg of iron — equivalent to several months of dietary intake. Regular donors should monitor ferritin and may benefit from low-dose iron supplementation.

Frequently Asked Questions