This study investigates the anti-diabetic effects of anthocyanin cyanidin-3-O-glucoside (C3G) on insulin-resistant hepatocytes and diabetic mice. C3G, extracted from red bayberry, was found to alleviate glucose metabolism disorders by increasing insulin sensitivity in hepatocytes. In vitro, C3G treatment increased glucose consumption, glucose uptake, and glycogen synthesis in insulin-resistant (IR) hepatocytes, which was associated with the inhibition of protein tyrosine phosphatase-1B (PTP1B) and increased phosphorylation of insulin receptor substrate-2 (IRS-2). In vivo, C3G supplementation in diabetic db/db mice reduced fasting blood glucose levels, improved glucose tolerance, and decreased insulin resistance. These findings suggest that C3G has potential as a natural dietary supplement to regulate glucose metabolism in type 2 diabetes mellitus (T2DM).This study investigates the anti-diabetic effects of anthocyanin cyanidin-3-O-glucoside (C3G) on insulin-resistant hepatocytes and diabetic mice. C3G, extracted from red bayberry, was found to alleviate glucose metabolism disorders by increasing insulin sensitivity in hepatocytes. In vitro, C3G treatment increased glucose consumption, glucose uptake, and glycogen synthesis in insulin-resistant (IR) hepatocytes, which was associated with the inhibition of protein tyrosine phosphatase-1B (PTP1B) and increased phosphorylation of insulin receptor substrate-2 (IRS-2). In vivo, C3G supplementation in diabetic db/db mice reduced fasting blood glucose levels, improved glucose tolerance, and decreased insulin resistance. These findings suggest that C3G has potential as a natural dietary supplement to regulate glucose metabolism in type 2 diabetes mellitus (T2DM).