Abstract Introduction The need for or the ideal length of the Biliopancreatic Bypass limb (BPL) length is a controversial topic. The Mini Gastric Bypass original technique (MGB-OT) version of the One Anastomosis Gastric Bypass (OAGB) includes a “Tailored” BPL length. This study aimed to investigate the 1 to 10-year outcomes of the “Tailored’ BPL length in patients undergoing MGB-OT in diabetic patients with Class III obesity. Methods The study is a retrospective chart review of 114 patients who underwent the Mini Gastric Bypass original technique (MGB-OT) with a tailored Biliopancreatic Limb length as described by Rutledge et al. These cases were performed between June 2008 and December 2009. The study investigated the relationship between the length of the BPLL and glycaemic control, primarily as measured by the change in (Delta) HbA1c levels, in morbidly obese diabetic patients undergoing the MGB-OT. The mean BPL length in the study was 185 cms, with a range of 120-350 cms. The study analysed preoperative, post-operative, and Delta HbA1c levels as the primary outcomes. The critical outcome goal for the study was HbA1c levels of less than 7%, which is a commonly used target for glycaemic control in diabetic patients. Results Only 89 of 114 (78%) patients completed the 10-year follow-up. The mean preoperative HbA1c was 9.2+/-1.6 (range 6.8-14.7). Longer BPL length were selected for patients based on a variety of patient factors including the patient’s preoperative HbA1c levels. Patients with longer BPL length had greater weight loss (R2 0.8.) The mean HbA1c levels were 5.50+/-0.36, 5.65+/-0.35, and 5.82+/-0.41 at 1, 5, and 10 years post-op. 100% of patients evaluated at 1 and 5 years had HbA1c levels below 7%, and only 1 out of 89 patients at 10 years had HbA1c levels above 7%. The correlation between BPL length and the 10-year Delta HbA1c was high, with a correlation coefficient (r) of 0.8. The Delta HbA1c was significantly greater in the patients with BPL length > 150 cm (3.99 +/- 1.87 vs 2.08 +/- 0.71 in the BP150 patients difference 1.91, SEM 0.40, 95% CI 1.12 to 2.69, P < 0.0001) i.e., longer BPL length (> 150cms) had significantly greater Delta HbA1c than 150 cm BPL length. Conclusions The study suggests that individualized tailoring of the biliopancreatic limb length in the OAGB procedure can potentially lead to a combination of excellent weight loss and near-complete normalization of HbA1c levels for up to 10 years. However, this a small and incomplete study and the optimal length may vary based on individual patient factors. Further research is needed to confirm these findings and establish standardized guidelines for determining the appropriate BPL length. Overall, the study highlights the importance and potential value of continued research and individualized treatment approaches for patients with obesity and diabetes.