Research Summary

High-dose vitamin D3 does not improve insulin resistance in type 2 diabetes

Moderate confidence

Low bias

Last updated June 19, 2026

Key Takeaway:

This study investigated the effects of high-dose Vitamin D3 supplementation on insulin resistance and glycaemic control in adult males with type 2 diabetes. It found no significant differences in key metabolic outcomes between the intervention and placebo groups.

Study at a Glance

What was studied

High-dose vitamin D3 supplementation in adult males with type 2 diabetes.

Participants

Young Adult (19–39), Middle Aged (40-64)

Male

with T2 Diabetes

Intervention

Vitamin D3 supplementation

Outcomes

Insulin resistance (HOMA-IR), Fasting Plasma Glucose (FPG), Plasma insulin, Glycated haemoglobin (HbA1c), Body mass index (BMI), Lipid profile, Serum 25-hydroxyvitamin D

Funding

Non-Industry Sponsored

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Main Effects

No statistically significant difference in insulin resistance (HOMA-IR) between groups at 24 weeks.

No significant difference in fasting plasma glucose levels at 24 weeks.

Vitamin D3 supplementation significantly increased serum 25-hydroxyvitamin D concentrations by 14.73 ng/mL (p=0.00012).

Evidence Summary

Intervention	Outcome	Measured Change	Study Effect
Vitamin D supplementation (Supplements)	BMI (Weight & Anthropometrics)	No Change	Unclear
Vitamin D supplementation (Supplements)	Fasting insulin levels (Metabolic Health)	No Change	Unclear
Vitamin D supplementation (Supplements)	Fasting Plasma Glucose (FPG) (Glycemic Control)	No Change	Unclear
Vitamin D supplementation (Supplements)	HbA1c (Glycemic Control)	No Change	Unclear
Vitamin D supplementation (Supplements)	Insulin resistance (Metabolic Health)	Increase	Unclear
Vitamin D supplementation (Supplements)	lipid profiles (Metabolic Health)	No Change	Unclear
Vitamin D supplementation (Supplements)	Serum 25-hydroxyvitamin D (Metabolic Health)	Increase	Strong

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Evidence Suggest

Vitamin D3 supplementation increased serum 25-hydroxyvitamin D levels significantly.
No significant changes were found in insulin resistance or glycaemic control.
The study's findings suggest limited effectiveness of high-dose Vitamin D3 for diabetes management.

Who this applies to

Adult males diagnosed with type 2 diabetes.
Patients seeking to manage diabetes through supplementation.

Keep in Mind

Results may not apply to women or younger populations.
The study did not measure long-term effects beyond 24 weeks.
Further research is needed to explore different dosages or combinations with other treatments.

Between the Lines

The study focused only on adult males, limiting generalizability to other populations.
No significant changes were observed in primary metabolic outcomes, raising questions about the intervention's effectiveness.
The duration of the study may not have been sufficient to observe long-term effects.

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Journal Reference

Muhammed HN, Bassam AH, Noordin O, et al. The Effect of High-Dose Vitamin D3 Supplementation on Insulin Resistance and Glycaemic Control in Adult Males with Type 2 Diabetes: A Double-Blind, Randomised, Placebo-Controlled Clinical Trial. Journal of Pharmaceutical Policy and Practice. 2026;19(1):2680824. doi:10.1080/20523211.2026.2680824

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Connected Evidence

Discover how this study fits into the broader diabetes evidence landscape.

This study contributes to evidence on Vitamins, Minerals, and Nutraceuticals and Serum 25-hydroxyvitamin D, Vitamins, Minerals, and Nutraceuticals and Glycemic Control.