How much iron do you need per day?

The RDA for iron is 8 mg a day for adult men, 18 mg for women aged 19–50, 8 mg for women 51 and over, and 27 mg in pregnancy.

These are the reference amounts used on US food labels and in dietary guidance, not personal targets. What you need shifts with age, pregnancy, medication and health conditions. The % Daily Value shown on every food page here is calculated against the FDA Daily Value for iron, which is 18 mg a day.

What this means for you

Iron is the nutrient where the number on the label and the number your body gets are furthest apart, so the daily figure on its own will mislead you.

From a mixed diet with meat, seafood and vitamin C, you absorb roughly 14 to 18 per cent of the iron you eat. From a vegetarian diet, 5 to 12 per cent. That gap is the reason the recommendation for vegetarians is 1.8 times higher. Plants are not short of iron. The iron in them is just harder to get at.

That gap shows up in the blood. Vegetarians carry about 30 micrograms per litre less ferritin than people who eat meat, and in men the difference is closer to 62. Ferritin is your iron store rather than a diagnosis, and these are snapshot studies that cannot prove the diet caused the difference. What they do justify is finding out where you stand instead of assuming.

The requirement itself splits sharply. Women aged 19 to 50 need 18 mg a day. Men, and women past fifty, need 8 mg. A menstruating woman needs more than twice what her father does, which is worth knowing before anyone compares plates at the same table.

What actually moves absorption

Vitamin C in the same meal as plant iron helps a lot. Lemon over lentils, peppers in the bean stew, fruit after porridge. Meat, poultry and seafood help too, and they help the plant iron sitting next to them on the plate, not only their own.

Unsettled. The vitamin C advice is shakier than its popularity suggests. When fruit rich in vitamin C was added to meals in trials, ferritin rose by about 9 micrograms per litre and haemoglobin by about 1.3 g/L. Both are small and both are real. Measured iron absorption, which is the mechanism everyone quotes for it, did not move at all. Something in the fruit helped. Nobody has shown it was the vitamin C.

Working against you are phytates in grains and beans, and polyphenols in tea, coffee and cocoa. Calcium is the awkward one, because it blocks both plant and animal iron. A large glass of milk is not the best partner for the one meal this week you were counting on.

Phytate is the one people try hardest to engineer away, and the short view says the effort works. Take the phytate out of white bread and the rise in blood iron over the next two hours doubles, 59 against 30 micrograms per 100 millilitres beside high-phytate wholemeal.

Myth. Soaking, sprouting and sourdough will fill an empty iron store. Across eight human trials the long view did not follow the short one. Iron status failed to improve, and in one twelve-week arm on low-phytate sourdough rye ferritin fell from 32 to 27 micrograms per litre with total body iron falling alongside it. Where taking the phytate out did pay off over months, there was added iron in the bread to take up. Do these things because they make grains easier to digest.

In real portions from this site, a cup of cooked lentils is 6.6 mg, a cup of cooked black beans is 3.6 mg, and a palm-sized piece of cooked beef is 2.2 mg in the form that absorbs best. None of those is a solution on its own. Iron comes together across a week of ordinary meals or it does not come at all.

Which is also why the milligrams on a label are only half the answer. Plant foods and fortified foods carry only the non-heme form, and it absorbs less well than the heme iron in meat, seafood and poultry. Spinach is the example the NIH names for that gap: strong on content, weak in practice, because oxalate holds the iron back.

Not for everyone. Do not start iron supplements because you feel tired. Tiredness has many causes, iron deficiency is diagnosed with a blood test, and iron you do not need does not sit harmlessly, because the body has no way to get rid of a surplus. If you suspect you are low, and real deficiency does cause fatigue and poor concentration, the next step is a test and not a bottle.

Unsettled. Even in pregnancy, where the case for iron is strongest, the US Preventive Services Task Force concluded that the evidence is not sufficient to weigh the benefits and harms of routine screening and supplementation. The data exist. The trials are not consistent enough to settle it.

To be fair to the other side of that argument, the pregnancy trials are the largest body of evidence iron has. A Cochrane review of 57 trials in 48,971 women found daily iron cut anaemia from 7.4 per cent to 4.0 per cent, and in women who were not anaemic to start with, 23 studies found one case of anaemia avoided for every ten women treated. What those trials did not show was much movement in how the birth went. The full review of that evidence is here.

One practical finding from the same literature is worth knowing if tablets make you feel awful. Pooling 22 trials in pregnancy, taking iron on alternate days instead of daily left haemoglobin only slightly lower, caused far fewer stomach side effects and was taken far more reliably, and the rate of anaemia came out the same.

Unsettled. Outside pregnancy that result does not repeat. Eleven trials in people with iron deficiency anaemia compared the same two schedules and counted side effects at the same rate either way, a risk ratio of 1.07, with haemoglobin 0.28 g/dL in favour of daily dosing. Certainty was rated very low for both. Alternate-day dosing is worth asking your doctor about. A promise that the nausea will stop is more than the trials have earned.

Not for everyone. Iron tablets look like sweets. Accidental overdose of iron products is a leading cause of fatal poisoning in children under six. If there is a child in the house, this is the one supplement that belongs out of reach and out of sight.

Written from the evidence cards and the data on this page, then checked back against the sources. Bioma Learn has no human medical reviewer at this time and we say so rather than invent one. Information, not medical advice. How we verify.

Foods highest in iron on this site

• Sesame seeds, whole, dried — 21 mg per 1 cup (116% DV)
• Oats, instant, fortified, plain, cooked fortified — 13.9 mg per 1 cup, cooked (77% DV)
• Sesame seed kernels, toasted — 9.96 mg per 1 cup (55% DV)
• Chicken, liver, all classes, cooked — 9.89 mg per 3 oz (55% DV)
• Corn flour, masa, white fortified — 9.69 mg per 1 cup (54% DV)

All iron sources ranked →

Full guide: Iron: why the number on the label is not the number your body gets