Vitamin D deficiency is common in adults with prediabetes, and observational studies link low serum 25-hydroxyvitamin D to higher glucose and insulin resistance. This narrative review summarises what randomised trials of vitamin D supplementation report for glycaemic control and progression to diabetes in prediabetic adults, together with the biological rationale, trial design issues, dosing and safety. Large prevention trials show a small, statistically uncertain benefit overall, while pooled analyses and smaller studies suggest advantage mainly in those who are deficient at baseline. Heterogeneity in dose, duration and outcomes limits firm conclusions. No new trial is reported; the article synthesises published evidence only.
No takes yet. Share an insight, caveat, or question.
Namara et al. (2026) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: