Iron supplements for breastfed babies: when to ask

What does the evidence say about iron supplementation for breastfed infants?

1. A newborn's iron stores at birth, roughly 75 mg per kilogram of body weight, typically run low by 4 to 6 months of age, while breast milk supplies only about 3 to 4.5 mg of iron per liter with roughly 10 to 20 percent of that actually absorbed. 1
2. Guidelines call for starting a source of iron, either 1 mg per kilogram per day of supplemental iron or iron-fortified infant cereal or pureed meat, at 4 months of age for babies who are exclusively or mostly breastfed, continuing until weaning onto iron-fortified formula or a varied solid-food diet. 2
3. Standard infant formula is fortified with about 12 mg of iron per liter, which generally meets a growing baby's needs on its own, so a formula-fed baby usually does not need a separate iron supplement layered on top of it. 3
4. Babies born preterm carry smaller iron reserves at birth and are usually started on supplemental iron earlier and at a higher dose, around 2 mg per kilogram per day beginning about a month after hospital discharge, continuing to 12 months under their care team's guidance. 2
5. A meta-analysis of trials giving breastfed infants 1 mg per kilogram per day of iron found a meaningful rise in hemoglobin, about 6.29 g/L, within 4 to 6 months of starting, with no significant difference in weight gain or height growth compared with infants who did not receive it. 1
6. Because low iron often causes no obvious signs in a baby, the CDC points to anemia screening around 12 months of age as the standard way to catch it, regardless of whether a baby has already been getting supplemental iron. 3
7. Hemoglobin testing alone is an imperfect screening tool: it catches an estimated 73 percent of iron deficiency anemia cases, and a low result correctly points to iron deficiency only 10 to 40 percent of the time in 12-month-olds, since other things can lower hemoglobin too. 4
8. An evidence review found the case for routine iron screening and supplementation in average-risk infants was graded as insufficient evidence, while supplementation for higher-risk infants, including those born preterm, at low birth weight, or in food-insecure households, was graded as moderately beneficial, meaning a baby's individual risk factors shape this decision more than a single blanket rule. 5

Iron guidance by feeding type, based on published pediatric guidelines