Background: During Ramadan month Muslims neither eat or drink from down to sunset. Islam exempts some Muslims from fasting including diabetic patients. However, many diabetic patients insist on fasting without proper medical advice. Objectives: To determine the clinical effects of Ramadan fasting on diabetic patients, to identify the underlying factors of these effects and to outline recommendations for safe fasting. Method: This follow up study recruited 284 Muslim diabetic patients from two hospitals in Qualubeya Governorate, of these; only 200 patients completed the study. The patients were assessed by a structured questionnaire sheet, diabetes symptom checklist, anthropometric measurement and blood samples were collected to measure fasting blood glucose, cholesterol, triglyceride, High Density Lipoprotein, Low Density Lipoprotein and glycated hemoglobin (HbA1C). Results: There was a statistically significant increase in five DM symptom domain scores at the end of Ramadan than before; neuropathic pain, psychological fatigue, cardiovascular, psychological cognitive function and hyperglycemia P