Research Summary

Analyzed using Evidence Intelligence™

High-Dose Vitamin D3 Does Not Improve Glycaemic Control in Type 2 Diabetes

Last updated August 24, 2026

Key finding

Serum 25-hydroxyvitamin D concentrations increased significantly from baseline.

This study evaluated the impact of high-dose Vitamin D3 supplementation on insulin resistance and glycaemic parameters in adult males with type 2 diabetes, finding no significant differences in most outcomes.

Quick read

Study at a glance

The essential study design details in one scan.

EvidenceScore™

Moderate

Study type

RCTs

Follow-up

Medium-Term (3–12 mo)

Risk of bias

Some Concerns

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Plain-language summary

What this paper says

A plain-language read of the study’s main message and where it applies.

Study focus

Clinical relevance

Understanding the effects of Vitamin D3 on diabetes management is crucial, as many patients seek alternative therapies. This study suggests that high-dose Vitamin D3 may not be effective in improving key metabolic parameters in type 2 diabetes, guiding clinicians in treatment decisions and patient expectations.

Keep in mind

Limited to adult males, which may affect generalizability. Short duration of 24 weeks may not capture long-term effects. No significant clinical improvements observed despite increased vitamin D levels.

Published in

Journal Reference

Publication details and source links for this paper.

Muhammed HN, Bassam AH, Noordin O, et al. The Effect of High-Dose Vitamin D3 Supplementation on Insulin Resistance and Glycaemic Parameters 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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Main Effects

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

No significant differences 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 network

How this study fits

Understand where this research contributes within the broader evidence network.

Evidence Context

This study contributes evidence to Vitamin D supplementation and BMI, Fasting Plasma Glucose (FPG), Fasting insulin levels, and 4 more.

This study contributes evidence to

Intervention

Vitamin D supplementation

Outcome

BMI

Evidence topic

Insulin Resistance

Primary intervention

Vitamin D supplementation

Primary outcomes

BMI
Fasting Plasma Glucose (FPG)
Fasting insulin levels

Evidence topics

Insulin Resistance Supplements and Nutraceuticals Fasting Blood Glucose Glycemic Control

Primary intervention

Vitamin D supplementation

Primary outcomes

BMI Fasting Plasma Glucose (FPG)Fasting insulin levels

Evidence relationships

Intervention and outcome relationships this study adds to the evidence network.

Evidence pairs

Relationships

Evidence topics

contributes_evidence

Editorial context

Why this study matters

See why this paper is useful beyond its individual results.

Evidence network role

This section describes how the study fits into the current evidence network. It does not determine whether an intervention works on its own.

Moderate contributionModerate confidenceNetwork score: 72

Why it is useful

Contributes to 7 evidence relationships
Includes primary outcome data
Linked to 6 direct semantic evidence topics

Topic contributions

Evidence topic

Contributes evidence

Evidence topic

Contributes evidence

Evidence topic

Contributes evidence

Evidence topic

Contributes evidence

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Primary evidence

Evidence topic

Insulin Resistance

matched_intervention_and_outcome

Related evidence

Evidence topic

Supplements and Nutraceuticals

Save evidence

Core evidence

Study findings

The primary outcomes reported in this study.

BMI

Vitamin D supplementation → BMI

Evidence Intelligence™

EvidenceScore™: Strong; Score 79 · Based on 3 studies
ImpactScore™: 67; Slightly Positive
ConsistencyScore™: 67; generally_consistent

Based on 3 studies

Add to Evidence Tracker

Fasting insulin levels

Vitamin D supplementation → Fasting insulin levels

Evidence Intelligence™

EvidenceScore™: 84; Strong
ImpactScore™: 70; Positive
ConsistencyScore™: 60; generally_consistent

Based on 5 studies

Add to Evidence Tracker

Fasting Plasma Glucose (FPG)

Vitamin D supplementation → Fasting Plasma Glucose (FPG)

Evidence Intelligence™

EvidenceScore™: Strong; Score 79 · Based on 4 studies
ImpactScore™: 63; Slightly Positive
ConsistencyScore™: 75; consistent

Based on 4 studies

Add to Evidence Tracker

HbA1c

Vitamin D supplementation → HbA1c

Evidence Intelligence™

EvidenceScore™: 82; Strong
ImpactScore™: 69; Positive
ConsistencyScore™: 60; generally_consistent

Based on 5 studies

Add to Evidence Tracker

Insulin resistance

Vitamin D supplementation → Insulin resistance

Evidence Intelligence™

EvidenceScore™: 84; Strong
ImpactScore™: 70; Positive
ConsistencyScore™: 60; generally_consistent

Based on 5 studies

Add to Evidence Tracker

lipid profiles

Vitamin D supplementation → lipid profiles

Evidence Intelligence™

EvidenceScore™: Emerging; Score 59 · Based on 1 study
ImpactScore™: 50; Neutral
ConsistencyScore™: unclear; Not enough independent studies

Based on 1 study

Add to Evidence Tracker

Serum 25-hydroxyvitamin D

Vitamin D supplementation → Serum 25-hydroxyvitamin D

Evidence Intelligence™

EvidenceScore™: 80; Strong
ImpactScore™: 93; Very Positive
ConsistencyScore™: 100; consistent

Based on 6 studies

Add to Evidence Tracker

Evidence Library

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Evidence Suggest

Vitamin D3 significantly increased serum 25-hydroxyvitamin D concentrations.
No improvement in insulin resistance or glycaemic control was found.
Findings suggest limited effectiveness of high-dose Vitamin D3 in diabetes management.

Who this applies to

Adult males aged 18-65 with type 2 diabetes.
Individuals seeking alternative treatments for diabetes management.

Keep in Mind

Results may not apply to females or other age groups.
Further research is needed to explore long-term effects of Vitamin D3.
The study focused on a specific population, limiting broader applicability.

Between the Lines

Limited to adult males, which may affect generalizability.
Short duration of 24 weeks may not capture long-term effects.
No significant clinical improvements observed despite increased vitamin D levels.

Evidence Library

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Connected Evidence

Explore related studies, evidence collections, and research questions.

Relationships organized using the Dediabetes Evidence Intelligence™ framework.

This study contributes to evidence on Vitamin D supplementation and Insulin Resistance, Vitamin D supplementation and Insulin Resistance.

Related evidence relationships

Explore in Evidence Explorer

This study contributes to the evidence on the following intervention-outcome relationships.

Supplements

Detailed evidence

Vitamin D supplementation → Insulin Resistance

Supplements

Evidence Intelligence™

EvidenceScore™: 84; Strong
ImpactScore™: 70; Positive
ConsistencyScore™: 60; generally_consistent

Based on 5 studies

View evidence

Supplements

Detailed evidence

Vitamin D supplementation → Insulin Resistance

Supplements

Evidence Intelligence™

EvidenceScore™: 84; Strong
ImpactScore™: 70; Positive
ConsistencyScore™: 60; generally_consistent

Based on 5 studies

View evidence

Supplements

Detailed evidence

Vitamin D supplementation → lipid profiles

Supplements

Evidence Intelligence™

EvidenceScore™: Emerging; Score 59 · Based on 1 study
ImpactScore™: 50; Neutral
ConsistencyScore™: unclear; Not enough independent studies

Based on 1 study

View evidence

Included in these evidence collections

Curated evidence collections and hubs this study is part of.

Insulin Resistance Evidence Hub

All studies measuring Insulin Resistance

5 studies

outcome_hub

Measures Insulin Resistance as a key outcome.

Vitamin D supplementation Evidence Hub

All studies on Vitamin D supplementation

5 studies

intervention_hub

Contributes to Vitamin D supplementation evidence base.

lipid profiles Evidence Hub

All studies measuring lipid profiles

1 studies

outcome_hub

Measures lipid profiles as a key outcome.

Recent Diabetes Research

Latest published studies

recency_collection

Published within the last 2 years.

Explore more in Evidence Explorer

Jump to pre-filtered views in Evidence Explorer.

All studies on Vitamin D supplementation and Fasting insulin levels

Intervention: Vitamin D supplementationOutcome: Fasting insulin levels

5 results

All studies on Vitamin D supplementation and Insulin resistance

Intervention: Vitamin D supplementationOutcome: Insulin resistance

5 results

All studies on Vitamin D supplementation

Intervention: Vitamin D supplementation

5 results

All studies measuring Fasting insulin levels

Outcome: Fasting insulin levels

5 results

All studies measuring Insulin resistance

Outcome: Insulin resistance

5 results

Questions answered by this study

Generated from the study's connected evidence using Evidence Intelligence™.

Does Vitamin D supplementation improve fasting insulin levels?

Strong Evidence

Vitamin D supplementation may improve fasting insulin levels.

ConsistencyScore™: Results are generally consistent across studies.

Ranked evidence signals

1
Fasting insulin levels
EvidenceScore™ Strong | EvidenceScore™ 83.8 | moderate positive | ConsistencyScore™ Generally Consistent | 1 study

Why this answer: This answer is based on a single supporting study.

Limitations

Only one supporting study is available.

View Full Evidence

Does Vitamin D supplementation improve insulin resistance?

Strong Evidence

Vitamin D supplementation may improve insulin resistance.

ConsistencyScore™: Results are generally consistent across studies.

Ranked evidence signals

1
Insulin resistance
EvidenceScore™ Strong | EvidenceScore™ 83.8 | moderate positive | ConsistencyScore™ Generally Consistent | 1 study

Why this answer: This answer is based on a single supporting study.

Limitations

Only one supporting study is available.

View Full Evidence

Does Vitamin D supplementation lower HbA1c?

Strong Evidence

Vitamin D supplementation may lower HbA1c.

ConsistencyScore™: Results are generally consistent across studies.

Ranked evidence signals

1
HbA1c
EvidenceScore™ Strong | EvidenceScore™ 81.9 | moderate positive | ConsistencyScore™ Generally Consistent | 1 study

Why this answer: This answer is based on a single supporting study.

Limitations

Only one supporting study is available.

View Full Evidence

Does Vitamin D supplementation improve serum 25-hydroxyvitamin d?

Strong Evidence

Vitamin D supplementation appears to improve serum 25-hydroxyvitamin d.

ConsistencyScore™: Results are consistent across studies.

Ranked evidence signals

1
Serum 25-hydroxyvitamin D
EvidenceScore™ Strong | EvidenceScore™ 80.4 | strong positive | ConsistencyScore™ Consistent | 1 study

Why this answer: This answer is based on a single supporting study.

Limitations

Only one supporting study is available.

View Full Evidence

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Next steps

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Evidence topics

Follow the topics this study contributes to.

Insulin Resistance Evidence Hub Supplements and Nutraceuticals Evidence Hub Fasting Blood Glucose Evidence Hub Glycemic Control Evidence Hub

Explore in Evidence Explorer

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All studies on Vitamin D supplementation and Insulin resistance All studies on Vitamin D supplementation and Serum 25-hydroxyvitamin D All studies on Vitamin D supplementation and Fasting insulin levels All studies on Vitamin D supplementation and HbA1c

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