The objective of this study was to assess the chronic effects of a bile acid sequestrant, colestimide, on glucose metabolism. After db/db mice were fed a diet containing colestimide or cholic acid (CA) for 12 weeks, we investigated the impact of these agents on glucose and lipid metabolism. Colestimide significantly reduced the elevated fasting blood glucose level (p<0.01), and CA even more markedly reduced fasting blood glucose. The blood glucose level after an oral glucose load was significantly lower in the CA group than in the control group, but the colestimide group showed no significant difference. The insulin response to a glucose load was abolished in the control and colestimide groups. A hyperinsulinemic-euglycemic clamp study revealed that colestimide significantly improved the GIR (p=0.013). Hepatic EGP and Rd were also improved by colestimide, suggesting that it alleviated insulin resistance by suppressing hepatic glucose production and increasing peripheral glucose usage. CA significantly increased both the weight and cholesterol content of the liver, while colestimide reduced these parameters. Colestimide suppressed hepatic gene expression of SHP, but enhanced SREBP2 expression. On the other hand, CA increased the expression of SHP and lipogenic enzymes such as ACC and SCD-1, but had no effect on SREBP2. The present study demonstrated that colestimide improves hyperglycemia and hyperlipidemia, as well as reducing the hepatic lipid content. In contrast, CA exacerbates hyperlipidemia and increases the hepatic lipid content, although it improves glycemic control. Thus, colestimide is a well-balanced drug for the treatment of diabetes mellitus.