Background: Type 2 diabetes mellitus (T2DM) affects a large and growing share of the world's population, and a substantial minority of patients — the majority in some South Asian, Middle Eastern and African settings — use herbal preparations alongside or instead of prescribed oral hypoglycaemic agents (OHAs). Whether such preparations are pharmacologically comparable to standard drugs remains contested.

Objective: To critically compare the antihyperglycaemic efficacy and safety of herbal single-drug and polyherbal formulations against standard OHAs, using published randomised evidence and quantitative syntheses rather than new primary data.

Methods: This is a narrative, critically appraised review of meta-analyses, systematic reviews and representative randomised controlled trials (RCTs) identified from MEDLINE/PubMed-indexed sources. No original patient data were generated; all effect estimates reported here are attributed to their published sources. Glycated haemoglobin (HbA1c) and fasting plasma glucose (FPG) served as the anchoring outcomes, with a reduction of 0.5% in HbA1c taken as the conventional threshold of clinical significance.

Findings: In an overview of 25 meta-analyses covering 18 plant-based remedies, Aloe vera leaf gel (mean difference [MD] -0.99%, 95% CI -1.75 to -0.23), psyllium fibre (MD -0.97%, 95% CI -1.94 to -0.01) and fenugreek seed (MD -0.85%, 95% CI -1.49 to -0.22) produced the largest HbA1c reductions; Nigella sativa, Astragalus membranaceus and the Chinese formulae Jinqi Jiangtang and Gegen Qinlian each lowered HbA1c by at least 0.5%. By comparison, metformin monotherapy lowers HbA1c by approximately 1.12% (95% CI 0.92-1.32) versus placebo. Point estimates for the best-performing botanicals therefore approach, but do not clearly exceed, first-line pharmacotherapy — while carrying far wider confidence intervals, shorter follow-up, weaker methodological reporting and no outcome data on microvascular or macrovascular endpoints. Serious adverse events were not reported in these syntheses, but pharmacovigilance data document undeclared synthetic hypoglycaemic adulterants in illicit herbal antidiabetic products, with associated hypoglycaemia and lactic acidosis.

Conclusion: Several botanicals demonstrate statistically and clinically meaningful glucose-lowering effects and are plausible adjuncts to lifestyle measures and conventional therapy. The available evidence does not, however, support substitution of herbal formulations for standard OHAs. Adequately powered, blinded, standardised-extract RCTs of at least 12 weeks' duration with active comparators and hard endpoints are required before equivalence claims can be entertained.