A 3-hour postprandial blood glucose test of 5.8 mmol/L is generally normal. Normally 3 hours postprandial blood glucose level will return to the fasting blood glucose level, i.e., 3.9-6.1 mmol/L. However, 3 hours postprandial blood glucose is not used as a diagnostic criterion for diabetes, and it is mostly recognized as random blood glucose. The current three-hour postprandial glycemic index is 5.8 mmol/L, which is considered to be within the normal range. However, if you test just once and the 3-hour postprandial glycemic index is 5.8 mmol/L, you cannot accurately determine whether it is normal or not, because an occasional or one-time test cannot be used as a diagnostic criterion for hyperglycemia. If the monitoring of the glycemic index is abnormal, above the normal range, or below normal, it is recommended to consult a doctor as soon as possible, and under the guidance of the doctor to re-test, and then according to the diagnosis of the results of targeted treatment.