A perceived concern about the side-effects, compliance, and potential toxicity of a daily regimen of iron supplementation generated research to assess the relative efficacy of weekly versus daily supplementation in pregnant women, adolescents, and children. A review of these studies concluded that both daily and weekly iron supplementation reduces the prevalence of iron deficiency and anemia, daily supplementation is more effective than weekly supplementation in increasing hemoglobin and ferritin, and while daily supplementation produces only a slightly higher average hemoglobin response (approximately 2gl-1) than weekly supplementation, its relative impact on reducing anemia risk is 34%, largely because daily supplementation is more effective at increasing low hemoglobin concentrations.
From the results of two other studies, in Bangladesh and Indonesia, that carefully monitored the number of iron tablets consumed, it appears that the size of the hemoglobin response to iron appears to depend on the total amount of iron consumed. In these studies, most of the hemoglobin response was produced by the first 20-50 tablets consumed. But more research is needed before recommendations can be made about consuming a fixed number of tablets over a defined period of time while permitting flexibility about the consumption interval (i.e., daily, two or three times per week, weekly, etc.).
Taken together, the available evidence suggests that iron supplements should be taken daily to treat iron-deficiency anemia, especially in pregnant women. Weekly supplementation may offer a more feasible preventive strategy, particularly if it reduces costs, improves compliance, and reduces side-effects; however, more information is needed to assess the relative effectiveness of daily versus weekly supplementation under program conditions.
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