What is Ferrous Sulfate: Uses, Warnings & Interactions

Updated May 14, 2025  •  Published Dec 30, 2020

Ferrous sulfate is an iron compound that is a common ingredient in iron supplements. Iron is an essential component of proteins in the blood that carry or store oxygen in the blood and muscles. A well-balanced diet should supply enough iron in the diet, but people take over-the-counter or prescription iron supplements to ensure adequate iron intake or treat iron deficiency. Although ferrous sulfate is a common and low-priced iron supplement, iron salts like ferrous sulfate are not as gentle on the digestive system as other, higher-priced iron compounds.

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Ferrous Sulfate overview

BRAND NAMES:

  • Enfamil Fer-in-Sol, Feosol, Ferret’s Iron Supplement, Fe-Vite, Slow Fe

Generic Names:

  • Ferrous sulfate

Uses:

  • Dietary supplement used to prevent or treat iron deficiency or iron deficiency anemia

Therapeutic Classes:

  • Iron supplement, nutritive agent

Forms:

  • Tablet, slow-release tablet, capsule, liquid

How it’s taken:

  • By mouth

What is Ferrous Sulfate used for?

Ferrous sulfate is an iron supplement used to ensure adequate daily iron intake. Healthcare professionals prescribe it to treat or prevent iron deficiency or anemia or to meet the increased iron needs of pregnant women.

What form(s) does Ferrous Sulfate come in

  • Healthcare providers measure doses and the strength of ferrous sulfate products based on the amount of iron (elemental iron) per dose, which is less than the ferrous sulfate amount (it will vary).

  • Some ferrous sulfate products give the elemental iron dose on the package, some just give the ferrous sulfate amount, and some give both. The table below gives both.

  • Tablet

    • 35 mg elemental iron

    • 45 mg elemental iron (145 mg ferrous sulfate)

    • 60 mg elemental iron (300 mg ferrous sulfate)

    • 65 mg elemental iron (200 mg dried ferrous sulfate)

    • 65 mg elemental iron (325 mg ferrous sulfate)

  • Slow-release tablets

    • 45 mg elemental iron (145 mg ferrous sulfate)

  • Capsule

    • 65 mg elemental iron (200 mg ferrous sulfate)

  • Drops/oral solution

    • 15 mg elemental iron (75 mg ferrous sulfate)/mL

    • 44 mg elemental iron (200 mg ferrous sulfate)/5 mL

    • 60 mg elemental iron (300 mg ferrous sulfate)/5 mL

What are common Ferrous Sulfate doses?

  • Recommended daily intake (elemental iron):

    • For adults 19–50 years of age: 8 mg/day for men and 18 mg/day for women

    • For adults 51 years of age and older: 8 mg/day for men

    • For pregnant women or girls 14–18 years: 27 mg/day 

    • For lactating women 19 years of age or older: 9 mg/day 

    • For lactating girls 14–18 years: 10 mg/day 

    • For children 14–18 years: 11 mg/day for boys and 15 mg/day for girls

    • For children 9–13 years: 8 mg/day

    • For children 4–8 years: 10 mg/day

    • For children 1–3 years: 7 mg/day

    • For children 7–12 months: 11 mg/day

    • For newborns to infants up to the age of 6 months: 0.27 mg/day (adequate intake)

  • For iron deficiency anemia: 

    • In adults: 100–200 mg elemental iron daily taken in divided doses

    • In children: 60–120  mg elemental iron daily, depending on age

  • To prevent iron deficiency during pregnancy: 30 mg elemental iron per day 

  • For breastfed infants:

    • Who are preterm or low birth weight: 2–4 mg/kg elemental iron per day given as drops to a maximum of 15 mg elemental iron/per day

    • Who receive insufficient iron from supplementary foods by age 6 months: 1 mg/kg elemental iron daily given as drops

Common Ferrous Sulfate prescriptions

  • FeroSul
    100 tablets bottle

  • FeroSul
    100 tablets box

  • FeroSul
    325 (65 fe)mg tablet

How to take Ferrous Sulfate

  • Follow the directions on the label. Do not exceed the recommended dose.

  • If you are taking ferrous sulfate under the direction of a doctor, do not take more medicine than prescribed or take it more often than instructed. Carefully follow your doctor's instructions about any special diet.

  • Taking this medicine on an empty stomach, 30 minutes before or 2 hours after a meal is best. Take the medicine with a full glass of water or fruit juice. 

    • If the dose upsets your stomach, try taking it with food.

  • How to take ferrous sulfate tablets:

    • Swallow the tablet whole with a glass of water or other liquid. Do not crush, break, or chew it.

    • Store ferrous sulfate tablets in a closed container at room temperature, preferably in a cool, dry place.

  • How to take ferrous sulfate capsules:

    • Swallow the capsule whole with a glass of water or other liquid. 

    • Store ferrous sulfate tablets in a closed container at room temperature.

  • How to administer ferrous sulfate drops or solution:

    • Shake the bottle well before administering a dose.

    • Use the calibrated oral syringe or dropper that comes with this medicine to measure doses. Do not use kitchen utensils.

    • Adults can take the dose directly in the mouth or mixed with water, juice, or other liquid.

    • For infants, dispense the dose into the child’s inner cheek. The dose can also be mixed with formula, juice, cereal, or other foods.

    • Store ferrous sulfate solution in a closed container at room temperature away from direct light. Do not freeze.

What to do if you miss a dose of Ferrous Sulfate

  • Take a missed dose when remembered. 

  • If you are taking one dose per day, take a missed dose on the day it was supposed to be taken. Skip it if it’s the next day and take that day’s dose.

  • If you’re taking more than one dose per day, take the missed dose when you remember it. If it’s too close to the next dose, skip the missed dose and take the next dose as scheduled. 

  • To avoid stomach discomfort or other side effects, do not take a double dose to make up for a missed dose.

Ferrous Sulfate contraindications

  • You should not use this medicine if you have had an allergic reaction to iron supplements or if you have:

    • Hemochromatosis (a condition in which your digestive system absorbs too much iron)

    • Hemosiderosis (excessive iron deposits in the body’s tissues)

    • Any type of anemia that is not caused by iron deficiency

Ferrous Sulfate warnings

  • Don’t take ferrous sulfate supplements until you talk to a doctor if you are pregnant, breastfeeding, or taking any medications.

  • You should also first talk to a doctor before taking iron supplements if you have:

    • Stomach or intestinal problems

    • Diabetes

    • An active infection

    • Porphyria

    • Other medical conditions

  • Make sure any doctor or healthcare provider who treats you knows that you are using this medicine. Iron supplements may affect the results of some important medical tests.

  • Iron can cause your stools to be darker in color. This is normal and is not a cause for concern unless you have other symptoms of a digestive system problem.

  • Ferrous sulfate liquid may stain your teeth. You can prevent these stains by mixing the medicine with water or other liquids (such as fruit juice or tomato juice) and drinking the medicine with a straw. To remove any iron stains, brush your teeth with baking soda or peroxide.

  • Accidental overdose of iron supplements is the leading cause of fatal poisoning in very young children. Keep ferrous sulfate supplements in childproof containers securely out of the reach of children.

Ferrous Sulfate interactions

  • Iron supplements can interfere with the body’s ability to absorb many different types of drugs, particularly antibiotics. If you are on prescription medications, talk to a doctor before taking ferrous sulfate supplements.

  • Tell any doctor prescribing new medications that you are taking ferrous sulfate or other iron supplements.

  • Do not take oral iron supplements by mouth if you also receive iron injections.

  • Avoid taking ferrous sulfate with:

    • Antacids

    • Milk

    • Calcium-containing products

    • High-fiber foods

    • Caffeine.

Ferrous Sulfate side effects

Serious side effects

Most serious side effects of iron supplements are due to overdoses or chronic overuse. Talk to a doctor if you notice any signs or symptoms of a possible serious side effect, including:

  • Black and tarry stools, blood in the stools, persistent abdominal pain, vomiting blood

  • Trouble breathing, wheezing, shallow breathing, difficulty breathing when lying down

  • Sleepiness, dizziness, confusion, lethargy, seizures, coma

  • Rapid breathing, rapid heart rate

  • Weakness, yellowing of the skin or eyes

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing

Less serious side effects

  • Nausea

  • Vomiting

  • Constipation

  • Diarrhea

  • Gas

  • Stomach discomfort

  • Metallic taste in the mouth

  • Change in stool color

Sources:

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