While the high prevalence of ID suggests that iron supplementation may be an efficacious means to improve Hb, it is not yet clear to what extent indicators of ID such as low sFt and high sTfR also predict response to and, more importantly, health benefits from the supplementation. Despite ID that warrants iron supplementation, there may be other factors that limit Hb response to iron supplementation, such as deficiencies of vitamin A, vitamin B12 or folic acid, and chronic infection