It notes that some religion rituals may heal the Diabetes Mellitus patients. This research was carried out to seek the effect of Ramadan fasting Muslim Ummah (community). It observed the patients those are suffering from chronic diseases such as Diabetes Mellitus (DM). In fasting patients did not eat and drink during 13.5- 14 hours. At the time of fasting that there will be changes such as: activity, diet, hours of work, activities at night as tarawih (night prayer) and tadarusan (Holy Quran Recital). To determine the effect of Ramadan fasting on body mass index in patients with type 2 diabetes mellitus, a prospective longitudinal study of the fasting month of Ramadan until the end of the fasting Ramadhan was done. It took 19 patients who had been diagnosed with type 2 diabetes at Adam Malik Hospital. The data collected by taking blood samples at the beginning and end of the fasting of Ramadan fasting. Data were analyzed using paired T- test, wilcoxon. From 19 patients with type 2 diabetes, as many as 13 respondents (68.4%) male sex with a mean age of 57.26 years. Statistical tests performed showed me significant value in BMI (p <0.05), Waist Circumference (p <0.05). There are significant value of BMI, Waist Circumference and blood fasting glucosa in patients with type 2 diabetes before and after Ramadan fasting.