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#30 Iron Deficiency Anemia in the Elderly: How much iron is enough?

In elderly adults with iron deficiency anemia (IDA), what is the appropriate dose of iron?

In elderly patients with iron deficiency anemia, low doses of iron raise hemoglobin similar to higher doses with considerably less adverse events in most patients. Options for dosing include ½ of a 300 mg ferrous gluconate per day or 2.5 mL of Fer-In-Sol syrup a day. Clinicians should work-up the cause of anemia as appropriate.

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A Randomized Controlled Trial (RCT) addresses this question. 
  • 90 anemic patients (mean age 85, 59% female) randomized to 15 mg, 50 mg or 150 mg of elemental iron per day.1   
    • At two months, there was no difference among the groups in hemoglobin or serum ferritin. 
      • Hemoglobin increased 14 g/dL in all three groups. 
    • Adverse events were significantly more common at higher doses. 
      • Number Needed to Harm (NNH) for 150 mg versus 15 mg. 
        • Abdominal cramps: NNH=2. 
        • Nausea/vomiting: NNH=2. 
        • Constipation: NNH=5. 
        • Drop-out due to adverse events: NNH=5. 
  • IDA is common in the elderly.2 
    • >10% have IDA at age 65 and >20% have IDA at age 85. 
  • IDA in older patients requires work-up for potential causes, including gastrointestinal malignancy.3   
  • In the very elderly (age 85), IDA carries an increased risk of mortality, hazards ratio 1.41 (1.13 to 1.76), in addition to the condition causing anemia.4 
  • In pregnant5,6 and non-pregnant young women7 recommendations are difficult. 
    • Low dose reduced adverse events6,8 but did not improve ferritin5,7 and hemoglobin6 as much as high dose.  High-dose (≥60 mg/day) also decreased the risk of low birth weight.9,10   
  • Iron is commercially available in 300 mg tablets. For dose conversion: 
    • Ferrous fumarate 300 mg = 99 mg elemental iron. 
    • Ferrous sulfate 300 mg = 60 mg elemental iron. 
    • Ferrous gluconate 300 mg = 35 mg elemental iron. 
  • For dosing to 15 mg of elemental iron per day consider: 
    • ½ of ferrous gluconate 300 mg tablet (or one every other day). 
    • 2.5 mL of Fer-In-Sol syrup a day or one dropper (1 mL) of the Fer-In-Sol drops daily. 
  • Taking iron on an empty stomach improves absorption.5 
updated jan 19 2018 by ricky

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  • Candra Cotton BSc Pharm
  • G. Michael Allan MD CCFP

1. Rimon E, Kagansky N, Kagansky M, et al. Am J Med. 2005; 118:1142-7.

2. Guralnik JM, Eisenstaedt RS, Ferrucci L, et al. Blood. 2004; 104:2263-8.

3. Ioannou GN, Rockey DC, Bryson CL, et al. Am J Med. 2002; 113:276-80.

4. den Elzen WP, Willems JM, Westendorp RG, et al. CMAJ. 2009; 181:151-7.

5. Milman N, Bergholt T, Eriksen L, et al. Acta Obstet Gynecol Scand. 2005; 84:238-47.

6. Zhou SJ, Gibson RA, Crowther CA, et al. Eur J Clin Nutr. 2009; 63:183-90.

7. Kianfar H, Kimiagar M, Ghaffarpour M. Int J Vitam Nutr Res. 2000; 70(4):172-7.

8. Reveiz L, Gyte GML, Cuervo LG, et al. Cochrane Database of System Rev. 2011; 10:CD003094.

9. Haider BA, Olofin I, Wang M, et al. BMJ. 2013; 346:f3443.

10. Peña-Rosas JP, De-Regil LM, Dowswell T, et al. Cochrane Database System Rev. 2012; 12:CD004736.

Authors do not have any conflicts of interest to declare.

Les auteurs n’ont aucun conflit d’intérêts à déclarer.