Quick answer

NIH gives 9 mg of iron a day while breastfeeding for women 19 and older, 10 mg for teens, and an upper limit of 45 mg. In a randomized trial of 114 nursing women, 27 mg of iron a day for about 3.5 months did not significantly raise markers of oxidative stress.^1,2

Key facts

NIH gives 9 mg of iron a day while breastfeeding for women 19 to 50 and 10 mg for teens, below the 27 mg for pregnancy.^1,3
The upper limit is 45 mg a day from food and supplements, and it applies while breastfeeding.^1,3
NIH says about 60% of women who are lactating use a supplement that contains iron.¹
In 114 nursing women, 27 mg of iron a day did not significantly increase oxidative stress markers over about 3.5 months.²
In 168 mothers, 80 mg of iron a day for four months did not change their own or their breastfed infants' iron blood markers.⁴

What NIH says about iron while nursing

NIH gives 9 mg of iron a day for breastfeeding women 19 to 50, and 10 mg for teens, which is below the 27 mg it gives for pregnancy and the 18 mg for women 19 to 50 who are not pregnant. It reports that about 60% of women who are lactating use an iron-containing supplement, and it describes no breastfeeding-specific harm from iron.^1,3

Pregnant women need 27 mg of iron a day. Breastfeeding women need 9 mg, or 10 mg if they are 18 or younger.^1,3

The upper limit for iron from food and supplements is 45 mg a day for anyone 14 or older and 40 mg for younger children. It was set to avoid stomach and bowel side effects, and doctors sometimes prescribe more for a while to rebuild low stores.^1,3

NIH adds that breast milk contains highly bioavailable iron, but that the amounts in milk are not enough for infants older than 4 to 6 months, which is a point about the baby's food and not about a supplement for the mother.¹

What do trials of iron in nursing mothers show?

In one randomized trial, 114 breastfeeding women took an iron-free prenatal vitamin and either 27 mg of iron or placebo for about 3.5 months. Hemoglobin changed by 1.4 g/L more with iron than with placebo, and ferritin changed in women without elevated inflammation markers. Markers of oxidative stress did not increase significantly.²

In a second, double-blind trial, 168 healthy mothers took 80 mg of iron a day or placebo for four months. Hemoglobin, serum iron and ferritin were similar in the two groups for the mothers and for their exclusively breastfed infants. The authors suggested a longer follow-up could show an effect.⁴

Both trials measured iron markers and a few safety markers. Neither was large enough to rule out rare harms, so they do not settle the question for every mother or infant.^2,4

What cautions apply while nursing?

The cautions are those of iron in general. High doses, especially on an empty stomach, can cause upset stomach, constipation, nausea, abdominal pain, vomiting and diarrhea. Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6, which is why the label warns to keep iron out of a child's reach.^1,3

Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6. Iron tablets and capsules must carry a warning to keep them out of children's reach and to call a doctor or poison control center after an accidental overdose.^1,3

People with hereditary hemochromatosis absorb too much iron, which builds up to toxic levels. NIH advises them to avoid iron and vitamin C supplements.^1,3

Who should ask a doctor about iron while breastfeeding

Women who lost a lot of blood in delivery or were told they had anemia, who should ask their doctor about a blood test and a plan before taking iron.⁵
Women thinking about iron beyond a prenatal vitamin, who should ask their doctor or pharmacist to check it against the 45 mg upper limit.^1,3
Women taking levothyroxine, levodopa, an antibiotic or an acid-reducing medicine.¹
Women asking about an iron infusion, which the sources checked do not address.

Questions people ask

Is an iron supplement safe while breastfeeding?

NIH gives 9 mg a day for breastfeeding women 19 to 50 and an upper limit of 45 mg, and describes no breastfeeding-specific harm. Two randomized trials in nursing women measured iron markers and a few safety markers. Ask your doctor.^1,2,4

Is iron infusion safe while breastfeeding?

The sources checked cover iron taken by mouth, not infusions, which is not a finding either way. Ask your doctor.¹

Are iron tablets safe when breastfeeding?

NIH says high doses can cause stomach and bowel side effects, and that iron tablets must carry a warning to keep them out of children's reach, because accidental overdose is a leading cause of fatal poisoning in children under 6. Ask your doctor about the right amount.^1,3

Does iron pass into breast milk?

NIH says breast milk contains highly bioavailable iron. In a trial of 168 mothers, 80 mg a day for four months did not change the infants' iron markers over that period.^1,4

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This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.