What is the recommended dose of iron sulfate (ferrous sulfate) for an adult patient with iron deficiency anemia?

Recommended Dose of Iron Sulfate for Iron Deficiency Anemia in Adults

For adults with iron deficiency anemia, the recommended dose is 50-100 mg of elemental iron once daily, which translates to one 200 mg ferrous sulfate tablet (containing 65 mg elemental iron) taken once daily. 1, 2, 3

Standard Dosing Regimen

• One ferrous sulfate 200 mg tablet daily provides 65 mg of elemental iron, which falls within the evidence-based therapeutic range 1, 2
• The FDA label confirms this standard dosing: one tablet daily, preferably after meals 4
• This is a fixed dose for all adults, not weight-based 2

Why Once Daily Dosing is Preferred

• Recent evidence shows that 60 mg of elemental iron taken once daily stimulates hepcidin levels, which reduces subsequent iron absorption by 35-45% when additional doses are given the same day 1
• Alternate-day dosing actually increases fractional iron absorption compared to twice-daily dosing, though this is not standard practice for treating established anemia 1
• Once-daily dosing provides similar overall iron absorption to twice-daily dosing while minimizing gastrointestinal side effects 1

Alternative Formulations (if switching is needed)

If ferrous sulfate is not tolerated, equivalent elemental iron doses from other salts include:

• Ferrous fumarate 322 mg tablet = 106 mg elemental iron 1
• Ferrous gluconate 300 mg tablet = 37 mg elemental iron (would need 2 tablets) 1

Important caveat: Switching between different traditional iron salts when side effects occur is not supported by evidence, as they have similar side effect profiles 2

Treatment Duration and Monitoring

• Continue therapy for approximately 3 months after hemoglobin normalization to adequately replenish iron stores 1, 2, 3
• Monitor hemoglobin response within the first 2-4 weeks of starting therapy 2, 3
• If hemoglobin fails to rise by at least 10 g/L after 2 weeks, this predicts treatment failure with 90% sensitivity and 79% specificity 2, 3
• After completing treatment, monitor blood counts every 6 months initially to detect recurrence 1, 2

When to Consider Higher or Alternative Dosing

• Twice-daily dosing (65 mg twice daily = 130 mg total elemental iron) may be used for more rapid correction of severe anemia, though this increases side effects 3
• Parenteral iron should be considered when oral iron is contraindicated, ineffective, or not tolerated 1, 2
• Blood transfusion is reserved only for severe symptomatic anemia or circulatory compromise 2

Common Pitfalls to Avoid

• Avoid modified-release or delayed-release preparations—they have reduced iron absorption and are less suitable for prescribing 1, 3
• Do not administer with tea, coffee, milk, or antacids, which reduce iron absorption 3
• Do not stop treatment when hemoglobin normalizes—continue for 3 additional months to replenish stores 1, 2
• If gastrointestinal side effects occur, consider taking with food, though this slightly reduces absorption 3