Takju lees extract is expected to be a promising material for functional food. This study was conducted in order to assess the glycemic index (GI) of Takju lees extract and its effects in an oral glucose tolerance test (OGTT). The GI for Takju lees extract was evaluated with 10 healthy young adults (Male 5, Female 5). OGTT was conducted in 20 male db/db mice, fed on a diet containing 2% Takju lees extract for 4 weeks. Those animals were subjected to OGTT after one oral administration of Takju lees extract at 2 g/kg BW. The GI of the Takju lees extract was measured at 97.97. The effects of the Takju lees extract on the oral glucose tolerance test in db/db mice evidenced no differences as compared to the control group. In conclusion, Takju lees extract is a high GI material, and it has no effect on blood glucose levels in a type II diabetic animal model. Further studies will be required to confirm its anti-diabetic effects.