Holy Basil Extract

Potential mechanisms. Lab and animal work suggests tulsi leaf extracts can (a) stimulate insulin secretion from β-cells, (b) reduce intestinal glucose absorption, and (c) exert antioxidant/anti-inflammatory effects that may modestly improve metabolic parameters. For example, fractions of tulsi leaf extract stimulated insulin release in perfused pancreas and islet models; other work points to effects on glucose uptake and digestion.

Human signal (small trials). The best-known human data are small randomized or controlled studies that found reductions in fasting and/or post-prandial glucose versus placebo or usual care, plus a recent meta-analysis that pooled RCTs and reported a statistically significant reduction in fasting glucose. Importantly, these trials are small and heterogeneous, so the overall certainty is low–moderate and tulsi should be considered adjunctive, not a replacement for standard care. PubMed

Authoritative overviews. Clinical summaries aimed at clinicians (Merck Manual) note a possible glucose-lowering effect but emphasize the evidence base is limited and largely small-scale. Merck Manuals

Dried leaf (whole herb) — classic RCT dose.

• A randomized, placebo-controlled, single-blind crossover trial in people with non-insulin-dependent diabetes used dried tulsi leaves 2.5 g/day, taken daily, and reported ~18% lower fasting glucose vs placebo during the tulsi period. This is the most-cited regimen from controlled human work. ResearchGate

As an adjunct to a sulfonylurea.

• A 90-day study compared glibenclamide alone vs. glibenclamide + tulsi; the combination group showed slightly larger improvements in fasting/post-prandial glucose and HbA1c. (Formulation was tulsi leaf alongside standard therapy; the paper does not standardize to a specific extract ratio.) ijlpr.com

Extract capsules (general safety/duration guidance).

• Medical references note holy basil leaf extract has been used safely short-term; a common reference amount is ~500 mg/day for 60–90 days, though diabetes-specific benefits at this exact dose are not well-characterized. (Many commercial products provide 250–500 mg extract once or twice daily; composition varies.) Merck Manuals

Practical, research-aligned way to trial it (with clinician oversight):

1. Start low with a standardized tulsi extract (e.g., 250–500 mg once daily with food), or the 2.5 g/day dried-leaf regimen if you and your clinician prefer the research precedent. Keep the rest of your regimen unchanged for the first 2–4 weeks. ResearchGate
2. Track glucose closely (fasting and 2-hour post-meal) and watch for hypoglycemia if you’re on agents like sulfonylureas, insulin, or GLP-1/GIP agonists. Merck Manuals
3. Reassess at 8–12 weeks. If no meaningful improvement (and no adverse effects), discontinue; evidence doesn’t support long-term use beyond ~8–12 weeks without medical review. Merck Manuals
4. Pick quality products. Because herbal products vary, choose brands that disclose the plant species (O. tenuiflorum/sanctum), plant part (leaf), and standardization; avoid proprietary blends that obscure dose. (General guidance from clinical references on supplements.) Merck Manuals

• Randomized, placebo-controlled, crossover trial (1996). Agrawal et al. Patients with type 2 diabetes received tulsi leaves vs placebo; fasting glucose fell by ~21 mg/dL (~17.6%) and post-prandial by ~15.8 mg/dL (~7.3%) during the tulsi period. PubMed
• Adjunctive trial with sulfonylurea (2012). Somasundaram et al. 90-day study comparing glibenclamide alone vs glibenclamide + tulsi; the combination produced larger drops in FBG, PPG, and HbA1c. (Open-access article.) ijlpr.com
• Meta-analysis of RCTs (2018). Jamshidi, da Costa, Cohen. Pooled RCTs of tulsi in adults with metabolic disease found a significant reduction in fasting glucose (and improvements in some lipid measures), while noting heterogeneity and small sample sizes. ScienceDirect
• Mechanistic lab work. Tulsi leaf extracts stimulated insulin secretion in multiple β-cell and pancreas preparations, supporting a plausible mechanism for glucose-lowering seen in human trials. Invalid URL