Fasting blood glucose of 7.8mmol/L after taking metformin in diabetic patients does not reach the control target, should be combined with whether the patient occurs complications and other underlying diseases and other factors to comprehensively analyze whether the patient’s condition is serious or not, can not be generalized. According to the latest diabetes prevention and treatment guidelines, fasting blood glucose of diabetic patients should be controlled within the range of 4.4~7.0mmol/L. Therefore, if fasting blood glucose of 7.8mmol/L fails to reach the control target, further dietary adjustments, exercise therapy, or adjustments to the therapeutic regimen should be made depending on the patient’s specific situation, and the severity of the patient’s condition can not be determined from the results of fasting blood glucose alone. Diabetes mellitus is prone to complications such as infectious diseases, ketoacidosis, hyperosmolar hyperglycemia syndrome, diabetic nephropathy, etc. Some patients may also have dyslipidemia, coronary artery disease and other underlying diseases, and the condition of patients with complications or underlying diseases is relatively serious. It is recommended that diabetic patients with fasting blood glucose of 7.8 mmol/L after taking metformin go to the endocrinology department of regular hospitals for detailed consultation.