Does high-dose vitamin D supplementation impact insulin resistance and risk of development of diabetes in patients with pre-diabetes? A double-blind randomized clinical trial

Diabetes Res Clin Pract. 2019 Feb:148:1-9. doi: 10.1016/j.diabres.2018.12.008. Epub 2018 Dec 21.


Aims: The aim of this study is to evaluate the effect of high-dose vitamin D on insulin sensitivity and the risk of progression to diabetes.

Methods: In this double-blind, placebo-controlled randomized clinical trial adults with pre-diabetes and vitamin D deficiency were randomly assigned to either vitamin D3 or placebo. Fasting plasma glucose (FPG), 2-h oral glucose tolerance test plasma glucose (OGTT PG), Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), and the rate of progression of glucose tolerance was compared.

Results: A total of 162 patients were randomized, from which 83 finished the 6-month follow-up (44 in intervention group and 39 in control group). In 6 months, serum 25-hydroxyvitamin D levels were significantly higher in the intervention group (36 ng/ml vs 16 ng/ml, P value < 0.001). There was no significant difference between FPG or 2H-OGTT PG in two groups. HOMA-IR score was significantly lower in the vitamin D group (2.6 vs. 3.1; P value = 0.04). The rate of progression toward diabetes was significantly lower in the intervention group (28% vs. 3%; P value = 0.002).

Conclusions: In patients with pre-diabetes and hypovitaminosis D, high dose vitamin D improves insulin sensitivity and decreases risk of progression toward diabetes.

Keywords: Diabetes; Insulin resistance; Prevention; Vitamin D.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Blood Glucose / drug effects
  • Diabetes Mellitus, Type 2 / blood
  • Diabetes Mellitus, Type 2 / pathology
  • Diabetes Mellitus, Type 2 / prevention & control*
  • Dietary Supplements
  • Disease Progression
  • Double-Blind Method
  • Female
  • Glucose Tolerance Test
  • Humans
  • Insulin / therapeutic use
  • Insulin Resistance*
  • Male
  • Middle Aged
  • Prediabetic State / blood
  • Prediabetic State / complications
  • Prediabetic State / diet therapy*
  • Risk Factors
  • Vitamin D / administration & dosage*
  • Vitamin D / blood
  • Vitamin D / pharmacology
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / complications
  • Vitamin D Deficiency / diet therapy*


  • Blood Glucose
  • Insulin
  • Vitamin D