A randomised controlled trial of high dose vitamin D in recent-onset type 2 diabetes

Diabetes Res Clin Pract. 2014 Dec;106(3):576-82. doi: 10.1016/j.diabres.2014.08.030. Epub 2014 Sep 28.


Aims: Vitamin D insufficiency has been associated with impaired pancreatic beta-cell function. We aimed to determine if high dose oral vitamin D3 (D) improves beta-cell function and glycaemia in type 2 diabetes.

Methods: Fifty adults with type 2 diabetes diagnosed less than 12 months, with normal baseline serum 25-OH D (25D), were randomised to 6000 IU D (n=26) or placebo (n=24) daily for 6 months. Beta-cell function was measured by glucagon-stimulated serum C-peptide (delta C-peptide [DCP], nmol/l). Secondary outcome measures were fasting plasma glucose (FPG), post-prandial blood glucose (PPG), HbA1c and insulin resistance (HOMA-IR).

Results: In the D group, median serum 25D (nmol/l) increased from 59 to 150 (3 months) and 128 (6 months) and median serum 1,25D (pmol/l) from 135 to 200 and 190. After 3 months, change in DCP from baseline in D (+0.04) and placebo (-0.08) was not different (P=0.112). However, change in FPG (mmol/l) was significantly lower in D (-0.40) compared to placebo (+0.1) (P=0.007), as was the change in PPG in D (-0.30) compared to placebo (+0.8) (P=0.005). Change in HbA1c (%) between D (-0.20) and placebo (-0.10) was not different (P=0.459). At 6 months, changes from baseline in DCP, FPG, PPG and HbA1c were not different between groups.

Conclusion: Oral D3 supplementation in type 2 diabetes was associated with transient improvement in glycaemia, but without a measurable change in beta-cell function this effect is unlikely to be biologically significant. High dose D3 therefore appears to offer little or no therapeutic benefit in type 2 diabetes.

Keywords: ACTRN 12611001023943; Beta-cell function; Glycaemia; Randomised trial; Type 2 diabetes; Vitamin D.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biomarkers / blood
  • Blood Glucose / metabolism
  • C-Peptide / blood
  • Diabetes Mellitus, Type 2 / blood
  • Diabetes Mellitus, Type 2 / complications*
  • Diabetes Mellitus, Type 2 / drug therapy
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Female
  • Follow-Up Studies
  • Humans
  • Hypoglycemic Agents / therapeutic use
  • Insulin / therapeutic use
  • Male
  • Middle Aged
  • Time Factors
  • Vitamin D / administration & dosage
  • Vitamin D / analogs & derivatives*
  • Vitamin D / pharmacokinetics
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / drug therapy*
  • Vitamin D Deficiency / etiology


  • Biomarkers
  • Blood Glucose
  • C-Peptide
  • Hypoglycemic Agents
  • Insulin
  • Vitamin D
  • 25-hydroxyvitamin D