Safety and Tolerability of Vitamin D Supplementation in the Vitamin D and Type 2 Diabetes (D2d) Study – A Randomized Trial in Persons With Prediabetes

The routine use of vitamin D supplements has increased substantially in the United States. However, the safety and tolerability of long-term use of high-dose vitamin D are unknown. We assessed the safety and tolerability of vitamin D3 at a dose of 4000 IU daily in the vitamin D and type 2 diabetes (D2d) trial. Persons with overweight/obesity and prediabetes without a recent history of nephrolithiasis, hypercalcemia, hypercalciuria, or other...