BackgroundGlucagon like peptide-1 (GLP-1), an incretin hormone, regulates glucose metabolism by inducing insulin secretion and suppressing glucagon secretion. The aim of the study is to assess the levels of fasting and post-prandial GLP-1 and their risk for T2DM. A case control study was conducted at the diabetes clinic Sanglah Hospital Denpasar Bali, involving 40 subjects who were native Indonesian citizens and 18–70 years of age. Twenty subjects were allocated as the case group (subjects with T2DM) and 20 subjects were allocated as the control group (subjects with normal glucose tolerance [NGT]). Both fasting intact GLP-1 (FGLP-1) and 60 minutes post-75 gram glucose loading intact GLP-1 (1hGLP-1) levels were measured.ResultsBoth fasting and post-prandial GLP-1 levels were significantly lower in subjects with T2DM than those with NGT (2.06 ± 0.43 vs. 2.87 ± 0.67 pg/L, p < 0.01; and 2.49 ± 0.60 vs. 3.42 ± 0.85 pg/L, p = 0.02; respectively). Low levels of FGLP-1 (OR, 13.5; p = 0.001) and 1hGLP-1 (OR, 5.667, p = 0.018), with no response after glucose loading (∆GLP-1), were a significant risk for T2DM. According to the ∆GLP-1, there was a tendency of decreasing response of GLP-1 after glucose loading among subjects with T2DM (∆ = 0.43 pg/L) compared to subjects with NGT (∆ = 0.55 pg/L).ConclusionFrom this study it can be concluded that levels of intact GLP-1 are an important risk factor for T2DM in the Indonesian population.