Ramadan is the month during which Muslims have to abstain from eating and drinking from dawn until dusk. According to Islamic Laws, children, sick patients, travelers, and women who are menstruating or nursing a baby are exempt from fasting. However, not all Muslims who are ill seek this exemption and insist on fasting in any case. The effect of fasting during the month of Ramadan on patients with renal impairment is still a matter of controversy. Therefore, the present study was initiated to determine whether fasting in Ramadan has harmful effects in renal recipients with mild to moderate impaired allograft function. We conducted a retrospective study on 16 kidney recipients with mild to moderate impaired renal allograft function (calculated glomerular filtration rate lower than 60 ml/min) who had fasted during Ramadan within September to October 2007. Recorded data for each patient before and after the month of fasting were body weight, body mass index, blood pressure, as well as urinalysis, and serum levels of blood urea nitrogen, creatinine, uric acid, blood glucose, electrolytes, lipids, and hemoglobin. The mean age was 45.7 ± 14.5 years, ranged from 21-74 years. There was no significant change in creatinine clearances (the mean values before Ramadan was 47.8 ± 11.2 ml/min vs. 49.7 ± 12.7 ml/min after the month of Ramadan, P=NS). Blood pressure was not significantly lowered after the month of fasting (SBP 131 ± 13 mmHg vs. 128 ± 11 mmHg, P = 0.08; DBP 80 ± 5 mmHg vs. 79 ± 6 mmHg, P=0.4). We did not find an increase of acute complication, acute rejection or ATN, during Ramadan. To our knowledge, this is the first report of impact of Ramadan fasting on kidney allograft in recipients with mild to moderate renal failure from Iran. Our study demonstrated that allograft function in kidney recipients was unaltered by Ramadan fasting. Transplant recipients must consult their doctor for the type and dosage of medicine, and diet and precautions to be taken during the month.