L-arginine Results in an Artificial Increase in Creatinine

L-arginine is a commonly available over-the-counter supplement. We report a 65-year-old man with a history of benign prostatic hyperplasia, hypertension, and obstructive sleep apnea who had an elevated serum creatinine level and normal cystatin C in the setting of L-arginine supplementation. After discontinuation of L-arginine, repeat testing showed normalization of serum creatinine, while cystatin C remained unchanged, thus demonstrating that L-arginine use can result in an artificial increase in serum creatinine.