Berberine and blood sugar
Berberine has trial evidence for blood glucose in type 2 diabetes, summarized in a systematic review and meta-analysis. The doses in those trials are drug-like, often split across the day, and the side effect is often diarrhea. Berberine affects drug metabolism. It is not an over-the-counter replacement for metformin, and it is not appropriate in pregnancy. Anyone on glucose-lowering prescriptions should involve the prescriber.
Berberine is sold as a metabolic supplement. The papers are closer to a drug trial than to a vitamin.
The glucose evidence
A systematic review and meta-analysis of berberine in type 2 diabetes reported lower blood glucose (PMID 30393248). The people in the included studies already had diabetes. The result does not say a healthy person with a normal A1C should start it for prevention, and it does not say berberine replaces prescribed treatment.
Why the dose is not casual
Trial regimens are hundreds of milligrams at a time, more than once a day. Cramping and loose stools are common reasons people stop. Berberine inhibits pathways that clear other drugs, so transplant drugs, anticoagulants, and other narrow-window medicines are a hard stop for self-experimentation. Dihydroberberine is a different molecule and does not inherit this meta-analysis.
Sources
- Effects of berberine on blood glucose in patients with type 2 diabetes mellitus: a systematic literature review and a meta-analysis. Endocr J. 2019. PMID: 30393248.