There are many publications on various complications of therapeutic starvation, but only few cases and of renal complications have been described. During starvation two characteristic changes in kidney function occur: a reduction in glomerular filtration rate by about 50% and a decrease in renal uric acid clearance by impairment of tubular uric acid secretion with consequent hyperuricaemia. During fasting ketone bodies compete with uric acid for a common tubular secretion site. The development of some of the renal complications described in the literature so far can be explained bal failure with uric acid nephropathy, renal ischaemia and pre-existing kidney disease have been published. Furthermore reversible salt-losing nephropathies were observed. It is essential in the prophylaxis of renal complications during fasting to ensure that a sufficient fluid intake is maintained and the urinary output is controlled. Before therapeutic starvation is commenced parameters of renal function (urinalysis, blood urea, serum creatine, serum uric acid) must be determined and then monitored at regular intervals. After starvation has commenced the administration of uricosuric agents must be avoided and intravenous pyelography is contraindicated.