Retaining blood donors is important. Up to 5% of new blood donors, however, are deferred because of low hemoglobin. Although donation intervals are set to minimize iron deficiency, low levels of iron are a problem in regular donors, and deferred donors often do not return.
A recent meta-analysis from the Cochrane Collaboration evaluated 30 randomized control trials (over 4700 blood donors), including 19 trials comparing iron supplementation to a control group. This analysis found that iron supplementation significantly reduced the number of donors deferred due to low levels of hemoglobin, both at the first donation and at subsequent donations (p<0.0001). Iron supplements also increased hemoglobin levels and iron stores. Iron supplements, however, caused adverse side effects in 29% of donors compared to only 17% of donors who took placebo pills. While minimizing iron deficiency is important for donor retention, adverse side effects and the risk of long-term iron supplements need further investigation.
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