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Anaemia - iron deficiency - Prescribing information
What issues should I consider before prescribing iron supplements?

  • Adverse effects of oral iron supplements are a common cause of non-compliance — 10% to 20% of people are thought to discontinue iron supplements because of adverse effects [Little, 1999].
  • Adverse effects are dose related and are therefore directly related to the amount of iron absorbed [Reveiz et al, 2007]. When equivalent amounts of elemental iron are compared, the incidence of adverse effects is no greater with ferrous sulphate than with other iron salts [Cox, 2003; BNF 54, 2007].
  • If adverse effects are troublesome, the following may help to minimize them:
    • Taking the iron supplement with or after food.
    • Reducing the dose frequency (i.e. one or two tablets daily).
    • Taking a different iron formulation or salt with a lower content of elemental iron (e.g. a ferrous gluconate).
  • Iron supplements are better tolerated when taken with or after food, however this may decrease iron absorption by up to two thirds [Little, 1999]. Although iron absorption occurs more readily when taken on an empty stomach, there is an increased likelihood of stomach upset [Killip et al, 2007].
  • Drug interactions may occur in people receiving oral iron supplements, resulting in reduced iron absorption or interference with other medicines [Little, 1999; WHO et al, 2001]:
    • Oral iron reduces the absorption of tetracyclines, quinolones, bisphosphonates, and zinc.
    • The absorption of oral iron is reduced by zinc, magnesium salts (e.g. in antacids), calcium (e.g. in milk and dairy products), tannins (e.g. in tea, coffee, and cocoa), and phytates (present in cereal grains, legumes, nuts, and seeds) [Killip et al, 2007].

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