To the Editor: Senna is widely used in laxatives, but the results of its misuse are not inconsequential. We describe a 36-year-old woman admitted with hypercalcaemia and renal failure. She had a 6-year history of anorexia nervosa and ingestion of 50–100 senna tablets daily for weight loss. Examination revealed clubbing of the fingers and toes, a body mass index (BMI) of 17.7 kg/m2 and postural hypotension. Laboratory findings on admission are shown in Box 1. Results of autoimmune studies and protein electrophoresis, and the serum angiotensin-converting enzyme level were normal. Parathyroid hormone-related peptide was absent. She had a bland urinary sediment, trace proteinuria (150 mg/24 h; reference range, < 150 mg/24 h) and a urine pH of 5.0 (physiological range, 4.5–8.0).