A blood glucose of 6.2 mmol/L is not sufficient for a diagnosis of diabetes mellitus, if it is a fasting blood glucose it needs to be combined with a 2-hour postprandial blood glucose, which may be impaired fasting glucose, and if it is a 2-hour postprandial glucose, it is within the normal range. Prediabetes includes impaired fasting glucose and impaired glucose tolerance. Prediabetes and diabetes are different stages of the same disease. Diabetes is diagnosed when fasting blood glucose is greater than or equal to 7.0 mmol/L or 2-hour postprandial blood glucose is greater than or equal to 11.1 mmol/L combined with diabetes-related symptoms. Fasting blood glucose 6.1-7.0mmol/L and 2-hour postprandial blood glucose less than 7.8mmol/l is impaired fasting blood glucose, and 2-hour postprandial blood glucose 7.8-11.1mmol/L and fasting blood glucose less than 6.1mmol/l is impaired glucose tolerance. If abnormal blood sugar is found, it is recommended to go to the hospital to check the fasting and 2-hour postprandial blood sugar, glycated hemoglobin, etc., so as to make a clear diagnosis and timely treatment under the guidance of the doctor.