Vitamin D and Reduced Fasting Blood Glucose Levels

Research synthesisLow evidenceSmall effect6 studies · 1 beneficial · 5 neutral · 0 harmful

Across 6 studies, 1 reported a small beneficial effect of vitamin D on reducing fasting blood glucose, while 5 found neutral results. The beneficial effect was observed in patients with metabolic-associated fatty liver disease (MAFLD), but evidence in other populations (obese children, PCOS, type 2 diabetes) was neutral. Effects were typically observed at 84 days of supplementation, though median study duration was only reported in 1 of 6 studies.

Studied populations: patients with MAFLD

Caveats: Only 1 of 6 studies showed a statistically significant beneficial effect, and many studies did not reach significance—effect may be smaller than the predominant direction suggests. The evidence base is small (only 6 studies), and conclusions should be considered preliminary.

Generated Jul 11, 2026

Doses used in studies

IU/day: 10,000 (median 10,000, IQR 10,000–10,000) — 1 study

Time to effect

Median: 2.8 months · IQR 2.8 months–2.8 months · Range 2.8 months–2.8 months — Reported in 1 of 6 studies

Safety in these studies

Overall tolerabilityReported
These findings support the effectiveness and safety of high-dose vitamin D supplementation in correcting vitamin D deficiency and reducing PTH levels in patients with T2DM
from: Impact of High Doses of Vitamin D on Specific Metabolic Parameters in Type 2 Diabetes Pati

6 of 6 papersPopulation:

Can vitamin D supplementation affect cardiometabolic factors in children and adolescence with overweight and obesity? A grade-assessed systematic review and meta-analysis of randomized controlled trials.
- 2025-11-25
- Meta-Analysis · n = 440
- BMC pediatrics 25(1)
- - Amir Hossein Faghfouri
  - Mahsa Mahmoudinezhad
  - Pedram Pam
  - Sanaz Barazandeh
  - Fatemeh Faramarzi
  - Yousef Mohammadpour
  - Vali Musazadeh
  - Shahsanam Gheibi
- PubMed: 41291584
- DOI: 10.1186/s12887-025-05795-2
9 Insights on
- Reduced Fasting Blood Glucose Levels
- High evidence
- Children
vitamin D supplementation no significantly improved ... FBS
Effect
Neutral
Effect size
Small
Significant
No
Effect of Vitamin D Supplementation on Metabolic Parameters in Patients with Metabolic-Associated Fatty Liver Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
- 2026-04
- Meta-Analysis
- The Journal of nutrition 156(4)
- - Bowen Yu
  - Junyan Liu
  - Fangfang Bu
  - Hongli Yan
  - Chen Chen
  - Yanfei Li
  - Yifei Sun
  - Yaqin Wang
  - Junhua Yuan
- PubMed: 41478593
- DOI: 10.1016/j.tjnut.2025.101314
9 Insights on
- Reduced Fasting Blood Glucose Levels
- High evidence
- Clinical
Pooled analysis demonstrated that vitamin D supplementation significantly reduced: FBG concentrations [-0.21; 95% confidence interval (CI): -0.41, -0.02]
Effect
Beneficial
Effect size
Small
Significant
Yes
A meta-analysis of the effects of vitamin D supplementation on endocrine metabolic and inflammatory markers in patients with polycystic ovarian syndrome.
- 2026-01-02
- Meta-Analysis
- Medicine 105(1)
- - Baohua Wu
  - Jun Yao
- PubMed: 41496027
- DOI: 10.1097/md.0000000000046892
12 Insights on
- Reduced Fasting Blood Glucose Levels
- High evidence
- Clinical
fasting blood glucose (FPG) ... were unaffected
Effect
Neutral
Effect size
Small
Significant
No
The effect of vitamin D2 on lipid profile, anthropometric indices, blood pressure, and inflammatory and glycemic biomarkers in humans: A systematic review and meta-analysis of randomized controlled trials.
- 2024-10
- Meta-Analysis
- Prostaglandins & other lipid mediators 174
- - Zhihong Zhou
  - Jiyuan Liu
  - Hui Zhang
  - Kousalya Prabahar
  - Benjamin Hernández-Wolters
  - Yuanhong Yuan
- PubMed: 39154789
- DOI: 10.1016/j.prostaglandins.2024.106883
12 Insights on
- Reduced Fasting Blood Glucose Levels
- High evidence
a non-statistically significant decrease in FBG (WMD: - 4.61 mg/dL, 95 % CI: - 14.71 to 5.47, P = 0.370)
Effect
Neutral
Effect size
Small
Significant
No
Dose
not specified
Impact of High Doses of Vitamin D on Specific Metabolic Parameters in Type 2 Diabetes Patients: A Prospective Biomedical Study.
- 2026-03-06
- Observational
- International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition 96(1)
- - Filip Max
  - Tomáš Tesař
  - Andrea Gažová
  - Juraj Smaha
  - Martin Jankovský
  - Dana Dudová
  - Peter Jackuliak
  - Martin Kužma
  - Juraj Payer
  - Ján Kyselovič
- PubMed: 41873102
- DOI: 10.31083/ijvnr46454
5 Insights on
- Reduced Fasting Blood Glucose Levels
- Low evidence
- Clinical
Other metabolic markers (HbA1c, FBG, calcium, and phosphorus) remained stable over 12 weeks.
Effect
Neutral
Effect size
Small
Significant
No
Dose
10,000 IU/day (Group A) or 960 IU/day (Group B) for 12 weeks
Quantum theories of consciousness: a critical review of feasibility, philosophical sufficiency, and empirical testability.
- 2026-04-29
- Review
- Frontiers in psychology 17
- - Xun Ma
  - Aoping Wang
- PubMed: 42137085
- DOI: 10.3389/fpsyg.2026.1730965
2 Insights on
- Reduced Fasting Blood Glucose Levels
- Low evidence
Null findings are scientifically important – do not omit a measured outcome just because the result was negative or non-significant.
Effect
Neutral
Effect size
Small
Significant
No

Vitamin D and Reduced Fasting Blood Glucose Levels

Can vitamin D supplementation affect cardiometabolic factors in children and adolescence with overweight and obesity? A grade-assessed systematic review and meta-analysis of randomized controlled trials.

Effect of Vitamin D Supplementation on Metabolic Parameters in Patients with Metabolic-Associated Fatty Liver Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

A meta-analysis of the effects of vitamin D supplementation on endocrine metabolic and inflammatory markers in patients with polycystic ovarian syndrome.

The effect of vitamin D2 on lipid profile, anthropometric indices, blood pressure, and inflammatory and glycemic biomarkers in humans: A systematic review and meta-analysis of randomized controlled trials.

Impact of High Doses of Vitamin D on Specific Metabolic Parameters in Type 2 Diabetes Patients: A Prospective Biomedical Study.

Quantum theories of consciousness: a critical review of feasibility, philosophical sufficiency, and empirical testability.