Ferrous Sulfate: Uses, How to Take, Dosage & Side Effects

Ferrous sulfate is a supplement that is prescribed for the prevention or treatment of iron deficiency anemia. This type of anemia can lead to symptoms such as excessive fatigue, memory loss or constant headache.

Iron deficiency anemia is often the result of low iron intake from the diet, increased iron needs, or conditions that make it difficult for the body to absorb iron, such as celiac disease or bariatric surgery.

Ferrous sulfate can be prescribed for children, adults, pregnant or breastfeeding women. It is sold in pharmacies in the form of tablets, drops or syrup, containing between 25 mg and 500 mg of ferrous sulfate.

Pouring pills from pill bottle into right hand

What it's used for

Ferrous sulfate may be prescribed to treat low iron levels, iron deficiency anemia and bleeding. It can also be recommended for conditions that require higher iron needs, such as pregnancy and breastfeeding.

Ferrous sulfate in pregnancy

The use of ferrous sulfate during pregnancy is generally indicated to reduce the risk of iron deficiency during pregnancy, as this condition can increase the risk for premature birth, low birth weight and low iron levels in the baby in the first months of life.

Ferrous sulfate for children

Ferrous sulfate for children is often recommended in the first year of life, when the risk for iron deficiency is greater. Iron deficiency in children can impair neurological development and learning, and is more common in premature babies or those born with low birth weight.

How to take and dosage

Ferrous sulfate should be taken orally preferably 1 hour before or 2 hours after a meal, as advised by your doctor.

The dosage of ferrous sulfate varies according to the patient's age, treatment goal and the dose of each supplement. Recommended doses are as follows: 

1. Ferrous sulfate drops 125 mg/mL

Ferrous sulfate at 125 mg/mL is equivalent to 25 mg of elemental iron for each mL of solution, and the doses in drops for the treatment of iron deficiency anemia vary according to age and include:


Daily dose for iron deficiency anemia

Maximum dose per day

Breastfed babies 0 to 6 months old (weighing between 2 and 6 kg, or 4.4 lb to 13.2 lb)

3 to 15 drops per day, calculated by the pediatrician according to the baby's weight

15 drops

Babies 7 to 12 months old (weighing between 6 and 10 kg, or 13.2 lb to 22 lb)

10 to 30 drops per day, calculated by the pediatrician according to the baby's weight

30 drops

Children 1 to 3 years old (weighing between 22 lb to 30.8 lb)

20 to 40 drops per day, calculated by the pediatrician according to the child's weight

40 drops

Children 4 to 6 years old (weighing between 30.8 lb to 44 lb) 

30 to 60 drops per day, calculated by the pediatrician according to the child's weight

60 drops

Children 7 to 10 years old (weighing between 44 lb to 66.1 lb) 

40 to 80 drops per day, calculated by the pediatrician according to the child's weight

80 drops

Children over 11 years old (weighing over 66.1 lb)

40 to 150 drops per day, calculated by the pediatrician according to the child's weight

150 drops

Pregnant or breastfeeding women

60 to 120 drops per day, calculated by the OB

120 drops

Ferrous sulfate should be taken together with foods that are vitamin C sources, such as oranges and cashews, to improve iron absorption. It is also important to avoid using this supplement together with foods with caffeine (such as coffee, mate tea and green tea) and calcium (such as milk and dairy products), because these nutrients reduce iron absorption.

Also recommended: Vitamin C Foods: 21 Foods, Supplements & How to Consume tuasaude.com/en/vitamin-c-foods

2. Ferrous sulfate 40 mg tablet

Coated tablets of 40 mg of ferrous sulfate can be prescribed for children between the ages of 6 and 12 years at a dose of one tablet, 3 times a day, or for adults at a dose of one tablet up to 4 times a day, taken after meals.

For babies, preference should be given to ferrous sulfate drops in doses prescribed by the pediatrician.

Side effects

Possible side effects with ferrous sulfate use include loss of appetite, diarrhea, nausea, stomach pain, vomiting, dark stools, abdominal pain and constipation. Furthermore, there may be darkening of the teeth, especially when using ferrous sulfate drops.

Does ferrous sulfate lead to weight gain?

Ferrous sulfate is used to treat anemia, a condition that, among other symptoms, also causes a loss of appetite. Therefore, this supplement can improve appetite, and promote weight gain in people with anemia.

However, ferrous sulfate itself has no calories and does not contribute to weight gain. Furthermore, one of the possible side effects of using ferrous sulfate is nausea and vomiting, which reduces hunger and the desire to eat in some people.

Contraindications for use

People with blood diseases such as thalassemia, sickle cell anemia, hemolytic anemia or hemochromatosis (which is a condition that causes increased iron levels in the body) should not use ferrous sulfate supplement. 

This supplement is also not recommended for those with a history of alcohol abuse, frequent blood transfusions, liver disease, gastric ulcers, chronic diarrhea and ulcerative colitis.