Diabetic patients are not allowed to smoke, smoking for diabetes is mainly harmful to the following points: First, smoking can cause blood sugar fluctuations, nicotine in tobacco will increase the secretion of catecholamines, catecholamines will cause blood sugar is difficult to control and obvious fluctuations. Second, smoking can cause small blood vessel constriction, resulting in hypertension. Third, smoking can damage the vascular endothelium, leading to the onset and development of atherosclerosis, aggravating heart, brain, kidney, nerve and other complications in diabetic patients. Fourth, smoking can accelerate the heart rate and affect the heart function of diabetic patients. Fifth, smoking can also affect the lung function of diabetic patients, leading to easy complications of respiratory infections, and even tuberculosis and many other respiratory diseases. Sixth, smoking can make diabetic patients, including lung cancer, the prevalence of a number of tumors significantly increased.