iron supplements

Last edited 09/2023 and last reviewed 10/2023

The idea behind iron supplements is to correct the anaemia and to replenish body iron stores (1).

  • ferrous are better absorbed than ferric salts.
  • replacement of iron pharmacologically requires between 120 and 180 mg of elemental iron per day.

A commonly used preparation is ferrous sulphate (ferrous sulfate 200 mg is equivalent to 65 mg elemental iron)(2)

  • patients who do not tolerate traditional doses, a lower dose may be as effective and better tolerated

  • suggested regimes for iron deficiency prophylaxis and treatment using ferrous sulfate (6):
    • adult
      • 200 mg once daily, reduced if not tolerated to 200 mg once daily on alternate days
    • by mouth using modified-release tablets
      • 325 mg once daily, reduced if not tolerated to 325 mg once daily on alternate days
    • by mouth using oral drops
      • 2-4 mL once daily, reduced if not tolerated to 2-4 mL once daily on alternate days

  • if using ferrous fumerate
    • tablets contain ferrous fumarate 210 mg (equivalent to 69 mg elemental iron) or ferrous fumarate 322 mg (equivalent to 106 mg elemental iron)
    • capsules contain ferrous fumarate 305 mg equivalent to 100 mg elemental iron
    • oral solutions contain ferrous fumarate 28 mg/mL equivalent to 9 mg/mL elemental iron

  • suggested regimes for iron deficiency prophylaxis and treatment using ferrous fumerate (6):
    • by mouth using tablets
      • adult
        • initially 210 mg once daily, reduced if not tolerated to 210 mg once daily on alternate days, alternatively initially 322 mg once daily, reduced if not tolerated to 322 mg once daily on alternate days
    • by mouth using capsules
      • adult
        • 305 mg once daily, reduced if not tolerated to 305 mg once daily on alternate days
    • by mouth using oral solution
      • adult
        • 6-11 mL once daily, reduced if not tolerated to 6-11 mL once daily on alternate days

A rise in haemoglobin concentration of around 0.1 g/dL per day (about 2 g/dL every 3 weeks) indicates effective treatment (but may vary from patient to patient) (2). Confirm treatment response by repeating haemoglobin levels at 2-4 weeks after starting iron supplements. If the response is

  • inadequate - could be due to a problem with adherence, malabsorption, or continuing blood loss, consider further investigations (1,4)
  • adequate - ensure that the haemoglobin level has returned to normal by a repeat blood count at 2-4 months (3)  

Oral iron should be continued for 3 months even after the iron deficiency has been corrected so that stores are replenished (1).

In patients who fails to respond to iron therapy or ones who are intolerant, the following parenteral preparations could be used:

  • iron sucrose - administered intravenously
  • ferric carboxymaltose - administered intravenously
  • iron (III) hydroxide dextran - administered either intravenously or by deep gluteal intramuscular injection

Anaphylaxis rates with IV iron therapy:

  • a study revealed that the adjusted incidence rates (IRs) for anaphylaxis per 10,000 first administrations were 9.8 cases (95% CI, 6.2 to 15.3 cases) for iron dextran, 4.0 cases (CI, 2.5 to 6.6 cases) for ferumoxytol, 1.5 cases (CI, 0.3 to 6.6 cases) for ferric gluconate, 1.2 cases (CI, 0.6 to 2.5 cases) for iron sucrose, and 0.8 cases (CI, 0.3 to 2.6 cases) for ferric carboxymaltose (5):
    • study authors concluded:
      • rates of anaphylaxis were very low with all IV iron products but were 3- to 8-fold greater for iron dextran and ferumoxytol than for iron sucrose

Check the respective summary of product characteristics for any drugs and doses described.

Reference: