Introduction: Iron deficiency anemia (IDA) is a common public health problem in adolescent girls. In Indonesia, the prevalence of IDA in adolescent girls reaches 37%. Iron tablets are an effective intervention to prevent and treat IDA.
 Methods: This research was a randomized controlled trial conducted on female senior high school students in Klaten, Indonesia. A total of 200 female students who met the criteria for anemia (hemoglobin levels < 12 g/dL) were randomized to receive iron tablets or placebo for 12 weeks.
 Results: At the end of the study, hemoglobin levels in the iron tablet group were significantly higher than those in the placebo group (mean difference 1.2 g/dL, 95% CI 0.8-1.6 g/dL). The prevalence of anemia in the iron tablet group was also significantly lower compared to the placebo group (20% vs 40%, p = 0.02).
 Conclusion: Giving iron tablets is effective in increasing hemoglobin levels and reducing the incidence of anemia in female senior high school students in Klaten, Indonesia.