This research aims to; (1) evaluate the effect of red betel leaves' extract in reducing the glucose level of mouse, (2) determine the effective extract dosage of red betel leaves.. The samples were gained by using random sampling technique. Moreover, the samples were divided into 4 groups, one controlling group and three experimental groups. In addition, the glucose was measured by glucometer. In addition, the glucose data was analyzed by using Anova one way test and continued to post hoc test.. The result of Anova test shown that p 0,001<A 0,05 so H0 was rejected. It meant that there was an effect of red betel leaves' extract in reducing the glucose level of mouse. The result of post doc shown that there was significant different on reducing glucose in every level of dosage tested.. The conclusion of this research was : (1) red betel leaves' extract significantly reduced the glucose level of mouse, (2) the dosage of 0,078 gr/20gr BB was already effective to reduce the glucose level of mouse.