Objective To compare the effects of sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) on body weight, glycemic regulation, and especially on anemia associated parameters. Methods A total of 107 obese patients who underwent metabolic and bariatric surgery in our hospital between December 2017 and July 2019 were studied retrospectively including SG(n=56) and RYGB(n=51). All patients took multi-vitamin and multi-mineral supplements postoperatively at a dose of 200% of daily suggested amount and vitamin B complex was additionally supplemented. Weight loss, diabetes remission and anemia related parameters were compared before and 3, 6 months after surgery. Results Age, sex, weight, and body mass index were comparative between two groups preoperatively. RYGB group had significantly more diabetes patients than SG group (88.2% vs. 25.0%, P<0.01). There was no significant difference in body weight loss between two groups. Percentages of total weight loss in SG and RYGB group were 26.92% and 22.20% (P>0.05), respectively. RYGB group had significant drop in glycosylated hemoglobin A1c than SG group at 6 months after surgery (2.31% vs. 0.69%, P<0.001), which indicated RYGB was effective in type-2 diabetes remission. No difference in anemia related parameters including hemoglobin, serum ferrum, ferritin, and folic acid after surgery was present between two groups. However, vitamin B₁₂ of the patients in RYGB group was 327.46 ng/L at 6 months after surgery indicating a strong dropping from 421.42 ng/L preoperatively. Conclusions RYGB was used much more for obese patients with 2 type diabetes when both SG and RYGB had robust effects on weight loss and beneficial outcomes in glycemic regulation. Anemia can be effectively prevented by supplementing vitamin and minerals and RYGB patients need even more supplement of vitamin B₁₂ and folic acid.