Most people can get enough iron from food, but how much you absorb depends on the type of iron and what you eat it with. This guide covers how much you need, which foods supply the most, how to absorb more, and who should get tested. Figures come from the NIH Office of Dietary Supplements, Iron fact sheet and the ICMR-NIN 2020 nutrient requirements.
Low iron is one cause of anaemia, and low B12 is another. See our vitamin B12 guide for the other side.
Quick Answer: How Much Iron Do You Need?
US adult men need 8 mg of iron a day and women aged 19 to 50 need 18 mg. India's ICMR-NIN 2020 figures are higher: 19 mg for men and 29 mg for women. The richest foods are fortified cereal, oysters, white beans and beef liver, and vitamin C helps you absorb the plant sources.
What Iron Does
Adults carry 3 to 4 g of iron, and most of it sits in haemoglobin, the protein in red blood cells that carries oxygen. The rest is stored as ferritin in the liver, spleen and bone marrow, or held in myoglobin in muscle. Transferrin moves iron around the blood, and the hormone hepcidin controls how much you absorb.
You lose only small amounts through urine, stool, sweat and skin. Menstruating women lose more through blood, which is why their requirement is higher.
How Much Iron You Need
Recommended Dietary Allowances (RDAs) from the NIH, in mg a day:
- Men aged 19 and over. 8 mg.
- Women aged 19 to 50. 18 mg. This drops to 8 mg from age 51.
- Teen girls aged 14 to 18. 15 mg. Teen boys need 11 mg.
- Pregnancy. 27 mg.
- Breastfeeding. 9 mg for ages 19 to 50, and 10 mg for ages 14 to 18.
- Children. 7 mg at 1 to 3 years, 10 mg at 4 to 8 years and 8 mg at 9 to 13 years.
India's ICMR-NIN 2020 RDAs are higher: 19 mg for adult men and 29 mg for adult women. ICMR-NIN also sets an estimated average requirement of 11 mg for men and 15 mg for women, and recommends using that figure for diet planning.
The NIH says people who follow vegetarian diets need about 1.8 times more iron than people who eat meat, because plant iron is absorbed less well.
Heme vs Non-Heme Iron
Meat, seafood and poultry contain both heme and non-heme iron. Plant foods and fortified foods contain non-heme iron only. Heme iron is absorbed better and is less affected by other foods on your plate.
The NIH puts iron bioavailability at about 14% to 18% from mixed diets that include meat, seafood and vitamin C, and 5% to 12% from vegetarian diets.
Iron-Rich Foods
Iron per serving from the NIH food table, against a Daily Value of 18 mg:
- Breakfast cereal fortified to 100% DV, 1 serving. 18 mg.
- Oysters, 3 oz cooked. 8 mg.
- White beans, canned, 1 cup. 8 mg.
- Beef liver, 3 oz pan fried. 5 mg.
- Lentils, boiled, half cup. 3 mg.
- Spinach, boiled, half cup. 3 mg.
- Firm tofu, half cup. 3 mg.
- Dark chocolate (45% to 69% cacao), 1 oz. 2 mg.
- Kidney beans or chickpeas, half cup. 2 mg.
- Sardines, 3 oz canned. 2 mg.
- Beef, braised bottom round, 3 oz. 2 mg.
- Cashews, 1 oz. 2 mg.
- Chicken, tuna or 1 large hard-boiled egg. About 1 mg each. See our guide to protein in an egg.
- Milk and cheese. Close to 0 mg.
The NIH notes that foods with 20% or more of the Daily Value count as high sources. Flour and cereal products are often fortified, and in the US about half of dietary iron comes from bread, cereal and other grain products.
Vegetarian and Vegan Iron Sources
Vegetarians can meet their needs, but the plan has to be deliberate because of the lower absorption. Build meals around beans, lentils, tofu, fortified cereal and nuts, and add a vitamin C food to each one. Our list of high protein foods overlaps heavily with these sources, and our guide to plant protein vs whey covers the powder side.
If you use a plant protein powder, check the label for iron per serving, since amounts vary by brand and are not a substitute for a food plan.
Boosting and Blocking Absorption
- Vitamin C. Ascorbic acid enhances non-heme iron absorption. Add lemon, tomato, peppers or fruit to bean and lentil meals.
- Meat, poultry and seafood. These also improve non-heme absorption when eaten in the same meal.
- Phytate and polyphenols. Phytate in grains and beans, and polyphenols in some plant foods, lower non-heme absorption. This is why spinach delivers less iron than its label suggests.
- Calcium. It might reduce absorption of both heme and non-heme iron, although the effect has not been definitively established. Experts suggest taking calcium and iron supplements at different times of day.
The NIH adds that these effects are attenuated by a typical mixed diet and have little effect on most people's iron status. They matter most if your intake is already marginal.
Signs of Low Iron and Testing
Iron deficiency develops in stages. Stores fall first, then the iron supply to red blood cell production drops, and finally iron deficiency anaemia appears with low haemoglobin. In the middle stage haemoglobin is usually still normal.
- Symptoms of iron deficiency anaemia. Weakness, fatigue, difficulty concentrating, stomach upset, and reduced immune function, cognition and exercise performance.
- Ferritin. Serum ferritin is currently the most efficient and cost-effective test. Below 30 mcg/L suggests iron deficiency and below 10 mcg/L suggests anaemia.
- Caveat. Inflammation, such as an infection, can raise ferritin and mask low stores.
- Haemoglobin. Haemoglobin and haematocrit are the most common screening tests, but the NIH calls them neither sensitive nor specific.
The WHO estimates that about half of the 1.62 billion anaemia cases worldwide are due to iron deficiency. The rest come from causes such as low B12 or folate, chronic infection and inflammation. See a doctor for a blood test before treating fatigue with supplements.
Who Is at Risk of Low Iron
- Pregnant women. Blood volume expands and the fetus needs iron.
- Women with heavy periods. At least 10% of menstruating women are thought to have heavy menstrual bleeding, which may account for 33% to 41% of anaemia cases in women of reproductive age.
- Infants and young children. Growth drives high needs, especially for preterm or low-birthweight babies.
- Frequent blood donors. About 25% to 35% of regular donors develop iron deficiency.
- Digestive conditions. Coeliac disease, ulcerative colitis, Crohn's disease and gut surgery raise the risk, and proton pump inhibitors can reduce absorption.
- Vegetarians and vegans. They rely on non-heme iron and need more of it.
- Heart failure and cancer. Both are linked with higher rates of iron deficiency.
Supplements and Safety
Iron supplements usually contain ferrous or ferric salts, and ferrous iron is better absorbed. Multivitamins for women typically give 18 mg, while iron-only products often give 65 mg. Check the Supplement Facts panel for elemental iron.
- Upper limit. 45 mg a day for adults. Doses of 45 mg or more can cause nausea, constipation and stomach upset, and taking iron with food reduces these effects.
- Zinc. Supplements with 25 mg of iron or more can reduce zinc absorption.
- Medicines. Iron can interact with levodopa and levothyroxine.
- Hemochromatosis. This inherited condition causes iron to build up. Treatment guidelines advise avoiding iron and vitamin C supplements.
- Children. Accidental iron overdose is a leading cause of fatal poisoning in children under 6, so keep supplements out of reach.
Do not start a high-dose iron supplement without a blood test. If you are pregnant, breastfeeding or on medicine, ask your doctor first. For related reading, see our protein powder for women guide.
Frequently Asked Questions
How much iron do I need per day?
In the US, adult men and women over 50 need 8 mg a day, women aged 19 to 50 need 18 mg, and pregnancy raises that to 27 mg. India's ICMR-NIN 2020 recommendations are higher, at 19 mg for adult men and 29 mg for adult women.
What are the best vegetarian sources of iron?
Fortified breakfast cereal (up to 18 mg a serving), canned white beans (8 mg a cup), lentils, tofu and spinach (about 3 mg per half cup each), plus chickpeas, kidney beans and cashews (about 2 mg each). Plant iron is non-heme, so it is absorbed less well than iron from meat.
Does vitamin C help you absorb iron?
Yes. The NIH lists vitamin C (ascorbic acid) as an enhancer of non-heme iron absorption, along with meat, poultry and seafood. Eating beans or lentils with a vitamin C food, such as lemon, tomato or peppers, is a practical way to use this.
Does coffee or tea block iron absorption?
Polyphenols in some plant foods, and phytate in grains and beans, reduce non-heme iron absorption. The NIH adds that in a typical mixed diet these effects are attenuated and have little effect on most people's iron status, so it matters most if you are already low.
Is spinach a good source of iron?
Spinach has about 3 mg per half cup boiled, but it also contains polyphenols that lower how much of that iron you absorb. It is a useful food, and a poor reason to rely on it as your only iron source.
Can you take too much iron?
Yes, from supplements. The upper limit for adults is 45 mg a day, and higher doses can cause nausea, constipation and stomach upset. Iron overload from food is rare, but people with hereditary hemochromatosis should avoid iron supplements unless a doctor advises them.
Which blood test shows low iron?
Serum ferritin, which reflects iron stores. The NIH says a level below 30 mcg/L suggests iron deficiency and below 10 mcg/L suggests iron deficiency anaemia, though inflammation can raise ferritin and hide a deficiency. Doctors usually combine it with haemoglobin and other tests.
The Bottom Line
US adults need 8 to 18 mg of iron a day, 27 mg in pregnancy, and India's ICMR-NIN figures are 19 mg for men and 29 mg for women. Fortified cereal, oysters, white beans, liver, lentils and tofu are the main food sources, and vitamin C with plant meals helps you absorb more.
If you are tired, have heavy periods, donate blood often or eat a vegetarian diet, ask your doctor for a ferritin test before supplementing. Too much iron is harmful.
This article is for general information and is not medical advice.
