Diabetes increases the risk of cancer. Diabetic patients have a high incidence of tumors, whether colorectal tumors, esophageal cancer, postmenopausal breast cancer, endometrial cancer, liver cancer, pancreatic cancer, and the incidence of these diseases is significantly higher than in non-diabetic patients. As to whether it is related to insulin in diabetes treatment, this question was first related to the long-acting insulin glargine insulin. However, the latest research has gone to deny this idea, so there is no uniform conclusion whether exogenous insulin stimulates insulin growth factor to trigger tumorigenesis. So at first the principle mastered was to avoid glargine insulin therapy for high risk patients with a family history of tumors, but the latest years seem to overturn this idea. However, whether insulin can actually cause tumors is an opinion that needs to be further confirmed by evidence-based medicine. It is important not to give up insulin therapy just because it causes tumors, knowing that more patients tend to use insulin therapy in advanced stages of the disease. If poor blood sugar control can aggravate the occurrence of colorectal cancer, endometrial cancer, breast cancer, liver cancer and other tumors, it will be more than worth the loss.