Clinical Edge

Summaries of Must-Read Clinical Literature, Guidelines, and FDA Actions

Vitamin D & Glycemic Control in Patients with T2D

J Clin Endocrinol Metab; 2017 Sep 1; Mirhosseini, et al

Vitamin D supplementation may significantly reduce serum fasting plasma glucose (FPG), HbA1c, and homeostatic model assessment of insulin resistance (HOMA-IR), a recent study found, while helping to control glycemic response and improve insulin sensitivity in patients with type 2 diabetes (T2D). The meta-analysis sought to determine the effect of vitamin D supplementation and improve vitamin D status on glycemia and insulin resistance patients with T2D. Researchers found:

  • 24 controlled trials with 1,528 patients with T2D were included.
  • There was a significant reduction in HbA1c (mean difference, -0.30%), FPG (mean difference, -4.9 mg/dL), and HOMA-IR (mean difference, -0.66), following vitamin D supplementation.
  • There was also a significant increase in serum 25-hydroxyvitamin D levels (overall increase of 17±2/4 ng/mL).


Mirhosseini N, Vatanparast H, Mazidi M, Kimball SM. The effect of improved serum 25-hydroxyvitamin D status on glycemic control in diabetic patients: A meta-analysis. J Clin Endocrinol Metab. 2017;102(9):3097-3110. doi:10.1210/jc.2017-01024.


Vitamin D deficiency is common among persons with type 2 diabetes.1 In observational trials, individuals with low vitamin D have an increased risk of developing diabetes.2 The question then is whether supplementation with vitamin D is effective at improving blood glucose control. In this large meta-analysis, it appears that vitamin D supplementation at a dose of 4000 IU per day does provide significant improvement in HbA1c outcomes. —Neil Skolnik, MD

  1. Mitri J, Muraru MD, Pittas AG. Vitamin D and type 2 diabetes: a systematic review. Eur J Clin Nutr. 2011;65(9):1005–1015. doi:10.1038/ejcn.2011.118.
  2. Song Y, Wang L, Pittas AG, et al. Blood 25-hydroxy vitamin D levels and incident type 2 diabetes: a meta-analysis of prospective studies. Diabetes Care. 2013;36(5):1422–1428. doi:10.2337/dc12-0962.