Generally the normal value of fasting C-peptide is 0.3~1.3mmo/L (the reference value range of different laboratories may be different), and the maximum value after meal can reach 4~5 times of fasting, so if 1.859mmo/L is measured in fasting, it belongs to the situation of high, but it is not necessarily necessary to take insulin, and it is necessary to combine with the glucose value to judge. Elevated C-peptide is common in insulin resistance, patients also need to improve the glucose tolerance test, glycated hemoglobin and other tests. Fasting blood glucose ≥ 7.0mmol / L, two hours after the meal or random blood glucose ≥ 11.1mmol / L, or glycated hemoglobin ≥ 6.5%, to meet any one of the clinical manifestations of “three more and one less”, can be diagnosed as diabetes. If the patient is clearly diagnosed with type 1 diabetes, insulin is required. If diagnosed with type 2 diabetes, oral hypoglycemic drugs such as metformin and acarbose can be chosen. If the diagnostic standard of diabetes is not met, but there is impaired glucose tolerance, the diet should be adjusted in time, low-salt, low-fat, low-sugar diet, along with moderate physical exercise. In addition, insulin is also suitable for patients with various serious acute and chronic diabetic complications, or type 2 diabetes mellitus with poor glycemic control by diet, exercise and oral medication alone, as well as special types of diabetes mellitus. Common adverse reactions include hypoglycemia, mild edema, blurred vision, allergic reactions, and fatty atrophy or hyperplasia. Insulin is a prescription drug and needs to be used under the guidance of a doctor.