Anemia is a body condition where the hemoglobin (HB) level in the blood is lower than normal. Young women are susceptible to anemia due to puberty, where the need for iron increases due to rapid growth, especially menstruation every month which causes them to lose a lot of blood. The aim of this research is to determine the relationship between knowledge of adolescent girls and measures to prevent anemia during menstruation at SMA Negeri 17 Medan. This type of research is observational analytic with a cross sectional design. The research sample was 63 out of 173 class XI female students. This research uses purposive sampling techniques and the Spearman test. The research results showed that the majority of respondents had good knowledge (52.4%) and had actions in the sufficient category (46.0%). The p-value is 0.000 (<0.05). Conclusion: There is a significant relationship between knowledge of young women and measures to prevent anemia during menstruation at SMA Negeri 17 Medan. Suggestion: It is hoped that young women will expand their knowledge regarding the prevention of anemia, especially the types, causes, driving factors and impacts of anemia by seeking information through books and other media and following programs implemented by the school UKS, as well as implementing healthy living behavior so that measures to prevent anemia increase. in a better direction