Abstract

Rita Mourya, Sarita Ahirwar, Bharti Patel, Prachi Raj, Akash Luniya

ABSTRACT

Background: Type 2 diabetes mellitus (T2DM) affects more than 800 million people worldwide, and a large proportion of patients use herbal medicines alongside conventional therapy. Despite widespread use, the comparative efficacy, mechanistic basis, and safety of antidiabetic botanicals have not been consolidated into a single clinically oriented synthesis graded for certainty. Objective: To systematically identify, appraise, and synthesise the highest-level evidence (meta-analyses, umbrella reviews, and randomised controlled trials) on the glycaemic effects, mechanisms of action, and safety of herbal medicines used in T2DM. Methods: PubMed, Scopus, Web of Science, EMBASE, and the Cochrane Library were searched from inception to January 2026, following PRISMA 2020. Eligible records reported glycated haemoglobin (HbA1c) and/or fasting plasma glucose (FPG) in adults with T2DM or prediabetes. Methodological quality was assessed with AMSTAR-2 and certainty of evidence with GRADE. Pooled weighted mean differences (WMD) with 95% confidence intervals (CI) were extracted and compared across botanicals. Results: Sixty-one studies were included, encompassing 27 quantitative syntheses covering 22 botanicals and more than 12,500 participants. Berberine produced the most robust reductions (HbA1c WMD ?0.63%, 95% CI ?0.72 to ?0.53; FPG ?0.82 mmol/L; moderate certainty). Silymarin (HbA1c ?1.07%), aloe vera leaf gel (?0.99%), psyllium (?0.97%), and fenugreek (?0.85%) showed the largest HbA1c reductions but with lower certainty, whereas ginger (?0.47%) and turmeric (?0.49%) achieved clinically meaningful reductions at moderate certainty. Nigella sativa lowered HbA1c by ?0.54% and FPG by ?24 mg/dL. Cinnamon reduced FPG consistently (?15 to ?25 mg/dL) without a reliable HbA1c effect. Serious adverse events were rare; the principal safety concern was additive hypoglycaemia and largely uncharacterised herb–drug interactions. Conclusions: Several botanicals — most notably berberine, ginger, and turmeric — achieve glycaemic reductions approaching those of first-line oral agents and may serve as evidence-informed adjuncts to standard care. High clinical heterogeneity, non-standardised preparations, and low methodological quality temper these findings. Herbal medicines should be used only as an adjunct to conventional therapy with monitoring for hypoglycaemia and herb–drug interactions.