This report presents the case of a rehabilitation inpatient with poor glycemic control and poor nutrition-related knowledge. Clinical Western medicine is used to treat diabetes mellitus (DM); however, the patient who had a nutrition-related knowledge deficit cannot effectively control blood sugar (BS). Thus, nutrition knowledge and skills are needed to improve BS. However, the patient verbalized unwillingness or disinterest in learning, so BS control was extremely poor. A simple meal plan, called the “diabetes plate method,” was modified to fit the nutritional guidelines of the American Diabetes Association and the Academy of Nutrition and Dietetics, which can be used as a guide to healthy eating in patients with DM.