The percentage of iron absorbed via the gastrointestinal tract varies greatly, from less than 1% to greater than 50%, depending on iron stores and need. Given that a substantial proportion of people experience GI side effects from oral iron, researchers in Israel evaluated whether low-dose iron therapy is as effective as standard-dose therapy among octogenarians with iron deficiency anemia. Ninety patients admitted to an inpatient service with hemoglobin levels between 8.0 g/dL and 11.9 g/dL and ferritin levels lower than 40 ng/mL were randomized to receive 15 mg, 50 mg, or 150 mg of oral iron daily.
At 2 months, serum levels of hemoglobin and ferritin had risen in all subjects; the 15-mg dose and the two higher doses led to similar increases. Abdominal discomfort occurred in significantly fewer subjects who received 15 mg (20%) than in those who received 50 mg (60%) or 150 mg (70%). Similarly, nausea, vomiting, diarrhea, and constipation were also more common among subjects in the two higher-dose groups.
In this small study among octogenarians, low-dose iron replacement was as effective as higher doses for treating iron deficiency anemia. Given the favorable side-effect profile of low-dose iron therapy, an empirical trial with a low dose seems appropriate for treating an older patient with iron deficiency anemia.
Reference:
Rimon E et al. Are we giving too much iron? Low-dose iron therapy is effective in octogenarians. Am J Med 2005 Oct; 118:1142-7.