Berberine is an AMPK-activating plant alkaloid studied mainly for glucose and lipid metabolism.
Across meta-analyses of 46 and 50 randomized trials, berberine is associated with HbA1c roughly 0.69 to 0.73 percentage points lower than control, with the clearest results when it is used alongside standard care rather than in place of it.
Lipid effects are smaller and less consistent than marketing suggests: the pooled LDL reduction in placebo-controlled trials is modest (-0.46 mmol/L, described by those authors as small), and in the largest hyperlipidemia meta-analysis, products containing berberine alone did not significantly lower LDL.
No measurable effect on blood pressure. Doses studied are most commonly 0.9 to 1.5 g/day, often 500 mg three times daily with meals, for 1 to 3 months.
Dihydroberberine reached roughly 6.7 times the 2-hour plasma berberine exposure of a 500 mg berberine dose in a 5-person crossover pilot, but that pilot found no accompanying difference in glucose or insulin.