Anemia is still one of the main unsolved global health problems, affecting 41.7% of preschool children (PSC). According to WHO, 50% of anemia cases are attributable to iron deficiency (ID). Based on these statements, most intervention programs use iron supplementation and/or iron food fortification. Nevertheless, anemia prevalence fell since 1990 until 2014, but then stagnated with a tendency to increase in the last years. Recent systematic studies suggest that the proportion of anemia cases attributable to ID is lower than previously assumed. In PSC, 25.0% of anemia cases from 23 countries and 30% from several Latin American countries were attributable to ID. There is no information reported of iron deficiency anemia (IDA) in PSC living in mountain areas. The importance of its study lies in the fact that around 350 million people live in altitudes over 1000m and asWHO recommends correcting hemoglobin by altitude, the prevalence of anemia increases dramatically...