The 3-hour postprandial blood glucose is generally not used as a criterion for determining diabetes mellitus, and the 3-hour postprandial blood glucose will mostly return to the fasting blood glucose level. A 3-hour postprandial blood glucose of 7.8 mmol/L with a slow decline may be due to delayed peak insulin secretion or insufficient secretion, and abnormal glucose tolerance or diabetes may exist. 1. Abnormal glucose tolerance: 3-hour postprandial blood glucose is mostly recognized as random blood glucose, and 3-hour postprandial blood glucose of 7.8mmol/L suggests that abnormal glucose tolerance may exist. However, the current conditions are not sufficient for diagnosis, and it is recommended that intravenous fasting blood glucose and 2-hour postprandial blood glucose measurements be performed under the guidance of a doctor to make a definitive diagnosis. 2. Diabetes mellitus: 3-hour postprandial blood glucose should generally return to the level of fasting blood glucose, i.e., 3.9-6.1 mmol/L, while the current 3-hour postprandial blood glucose is 7.8 mmol/L, suggesting the possible existence of diabetes mellitus, but not enough to confirm the diagnosis, it is recommended to consult the doctor in time, under the guidance of the doctor, combined with clinical symptoms, as well as fasting glucose, postprandial blood glucose 2 hours to determine. It is recommended that proper blood glucose measurement be performed under the guidance of a doctor for a definitive diagnosis and early treatment.