People with diabetes are often prone to hunger, and after quitting smoking, the appetite suppressant effect of nicotine is lifted and eating increases, thus causing weight gain. Quitting smoking also changes the intestinal flora, which can also lead to weight gain. However, the adverse effects of weight gain do not offset the favorable effects of smoking cessation. Therefore, physicians should encourage diabetic patients to quit smoking and focus on weight management during the cessation period. Follow-up visits (e.g., phone calls) for 6 to 12 months for successful quitters can help prevent relapse. Smoking cessation significantly reduces the incidence of cardiovascular disease and all-cause mortality in patients with diabetes. Smoking cessation also slows the progression of diabetic nephropathy. Smoking cessation increases HDL cholesterol levels and decreases LDL cholesterol, thus contributing to the prevention of diabetic complications. People with diabetes should quit smoking under the guidance of a medical professional.