The effects of Ashwagandha (Withania somnifera) supplementation on fasting blood glucose and HbA1c: a systematic review and dose-response meta-analysis of randomized controlled trials

Abstract

Ashwagandha (Withania somnifera) may affect glycemic control, although findings from randomized trials remain inconsistent. This systematic review and meta-analysis evaluated its effects on fasting blood glucose (FBG) and glycated hemoglobin (HbA1c). Cochrane Library, PubMed, Scopus, and Web of Science were searched from inception through August 12, 2026. Weighted mean differences (WMDs) and 95 confidence intervals (CIs) were estimated using random-effects models. Subgroup, meta-regression, nonlinear dose-response, sensitivity, and publication-bias analyses were performed, and evidence certainty was assessed using GRADE. Eleven trials involving 667 participants were included. Across 15 effect estimates, Ashwagandha modestly reduced FBG compared with placebo (WMD, -3.09 mg/dL; 95 CI, -5.61 to -0.58), with substantial heterogeneity. The HbA1c estimate, based on three trials, was imprecise and inconclusive (WMD, -0.05; 95 CI, -0.47 to 0.36). Exploratory subgroup analyses suggested variation in FBG effects by intervention duration and dose, but did not establish an advantage for any duration or dose. Nonlinear analyses showed no association with dose or intervention duration. Certainty of evidence was very low for both outcomes. Ashwagandha may modestly reduce FBG, but substantial heterogeneity and very low certainty preclude clinical recommendations.