OBJECTIVE To observe the effects of berberin on insulin sensitivity in high fat diet rats. METHODS Before and after ingesting berberin, glucose insulin tolerance test was used to measure the insulin sensitivity, and determining fasting blood glucose, insulin, blood lipid and muscle triglyceride content. RESULTS Compared with normal feeding rats, high fat feeding impaired insulin action (5.02 +/- 1.08 vs 8.72 +/- 0.91, P < 0.005), decreased liver glycogen level and raised fasting blood glucose, insulin and blood lipid levels. Berberin and metformin improved insulin resistance (6.31 +/- 0.95 and 6.24 +/- 0.65) and liver glycogen level in insulin resistance models, but had no effect on blood glucose, insulin, lipid levels and muscle triglyceride depots. CONCLUSION It is confirmed that berberin could raise insulin sensitivity of high fat diet rats similar to metformin.