Ferrous sulfate

Studies in people

• Concern

  Stomach and gut side effects³

  In adults, ferrous sulfate pills made stomach and gut side effects more likely than placebo or iron given into a vein.

• Open question

  Iron levels in toddlers⁴

  In toddlers given baby food with ferrous sulfate, hemoglobin did not clearly change.

• Concern

  Stomach upset in pregnancy⁵

  In pregnant women, ferrous sulfate raised iron levels but caused more belly pain and constipation than lactoferrin.

• Benefit

  Iron levels in kids⁷

  In schoolchildren with low iron, ferrous sulfate raised stored iron, and the rise lasted months.

• Benefit

  Iron levels in women⁸

  In women, ferrous sulfate raised iron stores more than a lower-dose iron supplement, with no gut differences.

• Benefit

  Iron levels in pregnancy⁹

  In pregnant women with anemia, ferrous sulfate raised iron levels and lowered a marker of oxidative stress.

• Benefit

  Iron absorption in infants¹⁰

  In infants, ferrous sulfate iron was absorbed better when given with a milk protein called apo-lactoferrin.

• Benefit

  Iron absorption in children¹³

  Kids absorbed more iron from ferrous sulfate in fortified food than from other iron sources tested.

• No harm found

  Iron absorption in women¹⁴

  In iron-depleted women, galacto-oligosaccharides did not boost how much iron the body took in from ferrous sulfate.

• Benefit

  Anemia in young children¹⁶

  In children 6 to 24 months old, ferrous sulfate plus folic acid cut anemia more than ferrous sulfate alone.

• Benefit

  Iron absorption in toddlers¹⁸

  In young children, ferrous sulfate mixed with NaFeEDTA helped the body absorb more iron from millet porridge.

• No harm found

  Gut bacteria in women¹⁹

  In Cambodian women, taking ferrous sulfate for 12 weeks did not change levels of a gut bacterium called Group B Streptococcus.

• Concern

  Stool oxidative stress²⁰

  In people, ferrous sulfate and other iron pills raised oxidizing waste in stool, and none of the three iron forms lowered it.

Animal and lab studies only

• Benefit

  Iron absorption from food²¹

  In lab studies, ferrous sulfate in strawberry-flavored plant-based yogurt gave more usable iron than the plain salt.

How it’s made and used

• Iron levels in the blood⁶

  In women, ferrous sulfate raised blood iron and free iron more than the other iron compounds tested.

• Iron supplement program for babies¹¹

  In babies in this program, few got ferrous sulfate as directed.

• Iron supplements in pregnancy¹²

  Almost all pregnant people in this study took ferrous sulfate, especially those over 30 and those who drank alcohol.

• Iron in the blood¹⁵

  In healthy men, ferrous sulfate raised a form of iron in the blood more than other iron pills did.

• Iron absorption from milk¹⁷

  In women, iron from ferrous sulfate was absorbed better than iron from the other compounds tested in milk.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.