Diabetes mellitus or commonly known as diabetes is a metabolic disease associated with unhealthy lifestyle patterns. Diabetes mellitus causes classic symptoms such as polyuria, polydipsia, fatigue and decreased physical performance, weight loss and causes complications. So that good management is needed with the four pillars of diabetes mellitus. The purpose of this case study is to look at knowledge and adherence related to the diabetes mellitus diet using the media booklet which is summarized with the 4 pillars of diabetes mellitus. This research began on 5-6 May 2023. The method in this study used a case study approach by implementing health education counseling related to the four pillars of diabetes mellitus. The sample in this study is Mrs. S. data collection was carried out by interviews, medical examinations, pre-tests, provision of health education, and ¬post-tests. The results of this case study are that with the measurements carried out giving the pretest and post-test there is an increase in knowledge and adherence to the diabetes mellitus diet in patients. It can be concluded that it is important to provide health education related to the 4 pillars of diabetes mellitus, especially people with diabetes mellitus in order to avoid the risk of complications that may occur and as an effort to increase knowledge and adherence regarding diabetes mellitus diet. One of the interventions that can be given to people with diabetes mellitus is the provision of health education related to the four pillars of diabetes mellitus which consist of: diabetes mellitus education, nutritional diet, pharmacology, and physical activity training