Vitamin C intoxication and hyperoxalemia in chronic hemodialysis patients.

We studied vitamin C levels in 25 stable patients on chronic hemodialysis who were taking 0.5-1 g vitamin C orally daily and/or dialyzed against dialysate containing 33.3 micrograms/ml of vitamin C. We also studied the relationship between serum vitamin C and oxalate levels in 7 patients on chronic hemodialysis. All patients had markedly elevated pre- and postdialysis levels of vitamin C. The predialysis levels of vitamin C showed extremely good correlation to the serum oxalate levels. Overingestion of vitamin C in food or as supplementation may lead to excessive serum levels of vitamin C, resulting in hyperoxalemia that may contribute to vascular disease in patients on chronic hemodialysis.