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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

Iron

The Oxygen-Carrying Mineral

Evidence grade 3 of 5, Mixed. Read how the Atlas grades evidence.

57 human trials, about 60 studies, Cochrane reviews + national surveys. The written rationale for this grade is still being prepared.

FDA
Regulated as a dietary supplement; also a prescription drug at treatment doses
WADA
Not prohibited

Reference only. Not medical advice.

What can go wrong

In the 2024 Cochrane review of daily oral iron in pregnancy, iron probably reduced iron-deficiency anemia at term from about 18 percent to 5 percent and probably lowered low birthweight, though certainty on several outcomes was low to moderate and there was no clear effect on preterm birth. For people without anemia, providing more than roughly the 27 mg RDA is not universally agreed on: the US CDC and ACOG back universal low-dose iron, while the USPSTF in 2024 found the evidence insufficient and the UK screens and treats rather than dosing everyone. The tolerable upper limit in pregnancy is 45 mg per day. Oral iron commonly causes constipation, nausea, and stomach upset, which limits adherence; the safe-storage point matters most, because iron-containing products have historically been a leading cause of poisoning deaths in young children and must be kept in child-resistant packaging out of sight and reach (see the iron-poisoning cross-reference). Iron should not be assumed beneficial in everyone: people with iron-overload conditions such as hereditary hemochromatosis are the standard exception. Whether to supplement, at what dose, and whether to use daily or intermittent dosing is a clinical decision. Bring anemia symptoms, existing conditions, and supplement choices to an OB, midwife, or other qualified prenatal provider rather than self-directing dose.

Iron carries oxygen in the blood, and pregnancy sharply raises the need for it as maternal blood volume expands and the fetus and placenta grow, roughly doubling iron demand across the pregnancy. Iron-deficiency anemia is the most common nutritional shortfall in pregnancy worldwide and is associated with preterm birth, low birthweight, and effects on the developing fetal brain. The pregnancy RDA rises to 27 mg per day. Guidance splits by setting: in the US the CDC recommends a universal low-dose supplement around 30 mg per day and ACOG recommends universal low-dose iron plus anemia screening, while the USPSTF concluded in 2024 that the evidence for routine screening and supplementation in people without symptoms is insufficient. WHO recommends 30 to 60 mg of elemental iron with folic acid for all pregnant women given the heavy burden in lower-income settings, and the UK (NICE, RCOG, British Society for Haematology) screens and treats rather than supplementing everyone. Treatment of diagnosed iron-deficiency anemia uses higher doses, on the order of 60 to 120 mg, which is a clinical decision.

Pregnancy roughly doubles iron demand to build maternal blood volume and supply the growing fetus, and deficiency is the most common nutritional shortfall in pregnancy worldwide.

What people take it for

These are the reasons people give for taking it. They are not effects it has been shown to have.

  • Building expanded maternal blood volume during pregnancy
  • Supporting fetal and placental growth
  • Preventing and treating iron-deficiency anemia in pregnancy
  • Supporting fetal brain development
  • Reducing the risk of low birthweight (2024 Cochrane review, moderate certainty)
  • Lowering entry into labor with anemia, associated with better tolerance of postpartum blood loss (FIGO 2025)

What people get wrong

  • Often saidEvery pregnant person needs a high-dose iron pill.

    ActuallyUS guidance recommends low-dose iron for routine use (the CDC specifies around 30 mg, near the 27 mg RDA), not high-dose, with treatment doses of 60 to 120 mg reserved for diagnosed iron-deficiency anemia. The tolerable upper limit in pregnancy is 45 mg per day, and NIH notes a meaningful share of US pregnant people already exceed it once food and supplements are combined. More is not automatically better and adds side effects.

  • Often saidIron supplements have to be taken every single day.

    ActuallySystematic reviews show intermittent regimens (for example, weekly or alternate-day elemental iron) can produce comparable outcomes with fewer side effects in some settings, which is why intermittent dosing is offered when daily iron is not tolerated. The choice belongs with a care team.

  • Often saidSupplementing everyone clearly improves birth outcomes.

    ActuallyThe 2024 Cochrane review found iron probably reduces iron-deficiency anemia and low birthweight, but showed little to no effect on preterm birth and rated overall maternal anemia as low-certainty. The USPSTF found no trials showing that routine screening and treatment in people without symptoms improves infant or maternal outcomes.

  • Often saidA person with hemochromatosis should still take routine pregnancy iron.

    ActuallyPeople with iron-overload conditions such as hereditary hemochromatosis are the standard exception to universal iron guidance and should not take routine iron without individualized advice, though iron deficiency can still occur in pregnancy and is managed case by case.

Who profits, and who pushes back

  • WHO & FIGO

    championsGlobal maternal-health bodies

    Routine iron and folic acid supplementation is recommended in pregnancy; anemia affects roughly a third of pregnant women globally and contributes to maternal and perinatal deaths, especially in lower-income countries.

  • CDC & ACOG

    endorsesUS public health and obstetric authorities

    Universal low-dose iron supplementation is recommended in pregnancy, alongside anemia screening at the first visit and again at 24-28 weeks, with treatment doses reserved for diagnosed iron-deficiency anemia.

  • U.S. Preventive Services Task Force

    mixedUSPSTF (2024 statement)

    Evidence is insufficient to fully assess the balance of benefits and harms of routine screening for and supplementation of iron-deficiency anemia in pregnancy; high-quality research linking maternal iron status to infant outcomes is still needed.

  • Practical-review obstetric literature

    caveatsClinical review, 2025

    Recommendations on screening and supplementation vary widely between countries; serum ferritin testing is generally reserved for the setting of anemia rather than universal screening.

Where the research comes from

Most of the published research on this comes from one place. 50% of it is from LMIC burden. Findings that no unrelated group has reproduced are weaker than the study count makes them look.

Share of published research by country of origin.
PlaceShare of published research
LMIC burden50%
Higher-income50%

Research published from: Global.

How we got here

Iron deficiency has been recognized as the leading cause of anemia for more than a century, and iron's importance in pregnancy reflects the large physiological rise in demand as maternal blood volume expands. Global attention has centered on lower- and middle-income regions of South Asia and sub-Saharan Africa, where anemia in pregnancy is most common and where WHO iron-folic acid programs have long been a core antenatal intervention. Guidance has since diverged by setting: the US moved toward universal low-dose supplementation, while the UK settled on screening and treating rather than dosing everyone. In 2024 the US Preventive Services Task Force reviewed the evidence and found important gaps, concluding that neither routine screening nor routine supplementation in asymptomatic pregnant people could be judged beneficial or harmful. The same year, an updated Cochrane review of 57 trials reaffirmed reductions in iron-deficiency anemia and low birthweight while lowering the certainty attached to several outcomes.

  1. 20th c.Iron deficiency established as the leading cause of anemia worldwide, including in pregnancy
  2. 2001US Institute of Medicine sets the pregnancy iron RDA at 27 mg/day and the tolerable upper limit at 45 mg/day
  3. 2010sWHO sets routine daily iron-folic acid supplementation (30 to 60 mg elemental iron) as a core antenatal intervention
  4. 2021ACOG Practice Bulletin 233 recommends universal low-dose iron plus anemia screening at the first visit and again at 24 to 28 weeks
  5. 2024USPSTF grades routine screening and supplementation for iron deficiency in asymptomatic pregnancy as I (insufficient evidence), August 20
  6. 2024Updated Cochrane review (Finkelstein, 57 trials, 48,971 women) reaffirms reduced iron-deficiency anemia and low birthweight, with low-to-moderate certainty
  7. 2025FIGO issues good-practice recommendations linking antenatal anemia to postpartum hemorrhage risk and endorsing routine iron, alone or within multiple micronutrient supplements

At a glance

Pregnancy RDA
27 mg/day
CDC low-dose supplement
30 mg/day
Treatment dose (anemia)
60-120 mg/day
Tolerable upper limit
45 mg/day

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about Iron. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.

Sources