ArticleTherapeutics and clinical risk management2026
Association Between Serum Vitamin D Levels and Metformin Efficacy in Obese Type 2 Diabetes Patients: A Retrospective Cohort Study Based on HbA1c Reduction.
Article in Therapeutics and clinical risk management, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
Purpose: To investigate the association between baseline serum 25-hydroxyvitamin D [25(OH)D] levels and glycemic response to metformin monotherapy in obese adults with type 2 diabetes mellitus (T2DM). Patients and Methods: This single-center retrospective cohort study analyzed the electronic medical records (January 2021-December 2023) of obese T2DM patients initiating metformin monotherapy. Participants were stratified by baseline 25(OH)D levels: deficiency (<20 ng/mL, n = 256) or sufficiency (≥20 ng/mL, n = 171). Propensity score matching (1:1) balanced covariates (age, sex, BMI, HbA1c, diabetes duration, comorbidities, season), yielding 142 matched pairs (n = 284). The primary outcome was absolute HbA1c reduction (ΔHbA1c) at 3 months. Multivariable linear regression, subgroup, and sensitivity analyses were performed. Results: In the matched cohort, vitamin D-sufficient patients achieved a clinically meaningful and statistically significant greater HbA1c reduction versus vitamin D-deficient patients (mean difference: 0.34%; 95% CI: 0.16-0.52%; p < 0.001). Baseline 25(OH)D positively correlated with ΔHbA1c (r = 0.32, p < 0.001). Multivariable regression confirmed that vitamin D sufficiency independently predicted greater ΔHbA1c (adjusted β = 0.41%, 95% CI: 0.22-0.60%, p < 0.001). Subgroup analyses revealed enhanced effects in females (p-interaction = 0.018), patients >60 years (β = 0.49% vs ≤60 years 0.33%, p-interaction = 0.009), and baseline HbA1c ≥8.5% (β = 0.56% vs <8.5% 0.21%, p-interaction = 0.003). Adverse events were comparable between groups. Conclusion: Higher baseline vitamin D levels (≥20 ng/mL) are associated with significantly improved metformin efficacy in obese T2DM patients, particularly among females, older adults, and those with poorer glycemic control. Vitamin D status may serve as a predictive biomarker for metformin response.
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