Are oral and intravenous vitamin C implicated in oxalate-associated renal failure? Exploring the role of pre-existing renal dysfunction

Vitamin C (ascorbic acid) degradation generates oxalic acid which has been implicated in oxalate-associated renal failure. The aim of this scoping review was to assess studies reporting an association of oral or intravenous (IV) vitamin C with acute renal failure presumed to be due to oxalate nephropathy to investigate the role of pre-existing renal dysfunction and other possible confounders of oxalate nephropathy. Of the 144 papers identified, 45 were included in the final review. These comprised 21 oral vitamin C case reports and 24 IV vitamin C case reports. Oral vitamin C cases were reported in people with pre-existing renal disease and/or gastrointestinal surgery or disorders leading to altered oxalate absorption, among other confounders such as dehydration and high dietary oxalates. IV vitamin C cases were reported in people with cancer, sepsis/burns, or other confounding conditions. In most cases, renal failure could be attributed to the primary disease and/or various medications and interventions used to treat the condition. Importantly, pre-existing renal dysfunction is a key risk factor for impaired clearance of large doses of vitamin C, thereby potentially contributing to hyperoxalosis and further renal damage. As such, it is vital for healthcare practitioners to monitor renal function both before and during high-dose vitamin C regimens.