β-cell glucose sensitivity (BCGS) improves after gastric bypass (RYGB) in individuals in diabetes (DM2) remission. We sought to assess BCGS (pmol/kg/min/mM) after an oral glucose test (OGT) and an IV graded glucose infusion (GGI) in subjects with and without DM2 remission after RYGB. Twenty five subjects with DM2 were studied with GGI and 75g-OGT before and 3 months after RYGB. Glucose, insulin, C-peptide, insulin secretion rate, GLP-1 and BCGS were assessed during the OGT and the GGI. Data are presented as mean±SD. Within and between group comparisons with paired and unpaired t-test; GLM with repeated measure to assess change during OGT or GGI were (SPSS 24). Of the 25 subjects studied pre-surgery, 10 experienced DM2 remission (REM), 9 remained with DM2 (N-REM) at 3 months; 6 remained glucose intolerant and were not included in the analysis. Pre-surgery BMI (41.5±4.7 kg/m2), weight (108.3±15.9 kg), age (43.8±8.8 years), gender (95% female), HOMA-IR (12.1±6.7) and Matsuda index did not differ between groups; N-REM had longer DM2 duration (14 vs. 2.5 y p<0.001), higher HbA1c (8.2±1.0 vs. 7.0±0.8%, p=0.01) and more likely to be taking insulin (7/9 vs. 0/10 p<0.001). Prior to RYGB, OGT-BCGS was 4x greater (0.83±0.60 vs. 0.22±0.24, p=0.01) and GGI-BCGS was 2.5x greater (0.48±0.30 vs. 0.18±0.15, p=0.04) in REM vs. N-REM. Weight loss did not differ for REM and N-REM (17±5%). HOMA-IR, GLP-1 and GGI-BCGS improved similarly in both groups. OGT-BCGS increased in both groups, but more in REM vs. N-REM (+1.31±1.0 vs. +0.30±0.28, p=0.01). The difference between OGT-BCGS and GGI-BCGS observed pre-RYGB (0.58±0.54 vs. 0.38±.035, p=ns) was exaggerated at 3 months by 4x in REM (2.13±1.vs. 0.58±0.15, p=0.001) and ∼2.5x in N-REM (0.60±.0.43 vs. 0.24±0.17, p=0.07). In conclusion, β-cell function assessed during an IV GGI improves by the same magnitude regardless of DM2 remission status after RYGB. However, β-cell function improved more in REM than N-REM after oral glucose, suggesting a greater incretin effect, or other gut-related mechanisms, in REM after RYGB. Disclosure A. Shah: Employee; Spouse/Partner; Daiichi Sankyo Company, Limited. K. Levesque: None. M. Ahlers: None. M.M. Holter: None. F. Alam: None. E. Pierini: None. B.L. Rojas: None. V. Mark: None. K. Patel: None. R. Dutia: None. E.J. Harvey: None. K. Park: None. N. Koshy: None. S.J. Belsley: None. J.J. Mcginty: None. B. Laferrere: None.