How much is too much? Two contrasting cases of excessive vitamin D supplementation.

BACKGROUND: In this report, we describe 2 contrasting cases of hypervitaminosis D.

CASE PRESENTATION: Patient 1 was a 75-y old man who developed symptomatic hypercalcemia (peak serum calcium concentration of 15.3mg/dl; reference range: 8.5-10.6mg/dl), cardiac injury, and a high total serum vitamin D concentration of 243ng/ml (30-80ng/ml) as a result of daily consumption of prescribed 50,000IU ergocalciferol (vitamin D2) and 500mg calcium-citrate for 1y. Patient 2 was a 60-y old woman who consumed 40,000IU of cholecalciferol (vitamin D3) daily for >10months with a peak total serum vitamin D concentration of 479ng/ml (30-80ng/ml), but did not present with symptoms related to vitamin D toxicity.

CONCLUSION: These cases demonstrate that individual responses to supraphysiologic concentrations of vitamin D for extended periods of time vary widely, and that defining a toxic concentration of this vitamin is difficult. The different outcomes in these two patients, despite months of high-dose vitamin D therapy, demonstrates that individual patient pharmacodynamics determine clinical sequelae.