Recently, Brethauer et al. (1) reported that bariatric surgery improved HbA1c in obese patients with type 1 diabetes. However, our data and existing literature demonstrate that improvement in glycemic control is not universal. We reviewed case files of six obese female patients with type 1 diabetes who had bariatric surgery. Mean age was 36 ± 7.8 years, median duration of diabetes was 18 years (range 2–31), and median follow-up from surgery was 16 months (range 7–119). Baseline weight was 124.7 ± 15.7 kg and BMI was 46.4 ± 8.4 kg/m2. Weight loss was 24.3 ± 1.9% of baseline and BMI reduction was 11.4 ± 2.7 kg/m2. There was no overall reduction in HbA1c following surgery (8.1 ± 1.3% [65 ± 14 mmol/mol] at baseline vs. 8.2 ± 1.6% [66 …