Fasting blood sugar 7.91mmol/L is not normal. The normal range of fasting blood glucose in normal human body is 3.9~6.0mmol/L, blood glucose ≥7.0mmol/L with diabetic symptoms should be considered as diabetes mellitus. Therefore, when the fasting blood glucose is 7.91mmol/L, it is recommended to improve the OGTT test, glycated hemoglobin and other related tests to clarify the diagnosis. For diabetic patients, the goal of glycemic control is generally in the fasting blood glucose 4.4mmol/L ~ 7.0mmol/L, 7.91mmol/L belongs to the glycemic control does not meet the standard, and it is not normal. Sugar control goals should also be set according to individual circumstances. If fasting blood glucose of 7.91mmol/L is found, it is recommended to consult a doctor in time, make a clear diagnosis, and carry out the correct glucose-lowering treatment (diet, exercise, medication, etc.) under the guidance of the doctor.