(HealthDay News) — For patients with prediabetes or diet-treated type 2 diabetes, high-dose vitamin D treatment has no effect on β-cell function, insulin sensitivity, or glycemic control, according to a study published online in Diabetes Care.

Henrik Wagner, MD, from the Karolinska Institutet in Stockholm, and colleagues randomized 44 subjects with prediabetes or diet-controlled type 2 diabetes to 30,000 IU vitamin D3 once weekly or placebo for 8 weeks. First phase (0 to 12 min) and second phase (12 to 120 min) insulin response, insulin sensitivity, and disposition index were assessed with a hyperglycemic clamp. Glucose tolerance and glycemic control were also examined.

Twenty-one subjects in the vitamin D group and 22 in the placebo group completed the study. The researchers found that the active treatment group had a 2-fold increase in the season-adjusted 25-hydroxyvitamin D levels. Compared with placebo, vitamin D treatment had no effect on first-phase or second-phase insulin secretion. No group differences were seen in insulin sensitivity, disposition index, or any measures of glycemic control. Compared with placebo, there was no hypercalcemia or other adverse effects of vitamin D treatment.

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“According to the findings of our study, we see no implication for vitamin D treatment to affect glucose homeostasis in subjects with abnormal glucose tolerance,” the authors write.

Renapharma contributed to independent monitoring and Merck contributed study medication.


  1. Wagner H, Alvarsson M, Mannheimer B, Degerblad M, and Östenson CG. No Effect of High-Dose Vitamin D Treatment on β-Cell Function, Insulin Sensitivity, or Glucose Homeostasis in Subjects With Abnormal Glucose Tolerance: A Randomized Clinical Trial. Diabetes Care. doi:10.2337/dc15-1057.