Berberine is a natural plant alkaloid found in goldenseal, barberry, goldthread, and Oregon grape. This well-tolerated extract works at the cellular level to support normal responses. In vitro evidence suggests Berberine works by helping to enhance AMPK-activated protein kinase. One study showed that 1,500 mg of Berberine daily supports normal responses after meals along with 3-month averages. Doctors' Preferred Berberine is backed by Triple-Testing Philosophy, which includes rigorous screening of raw materials, finished goods batch testing, and independent third-party lab testing. The result is a stellar 30-year reputation for outstanding quality and safety.