A blood glucose of 5.6mmol/L is generally not prediabetic, so there is no such thing as “why is a blood glucose of 5.6mmol/L prediabetic”. Prediabetes includes impaired fasting blood glucose and impaired glucose tolerance, when fasting blood glucose is greater than or equal to 6.1mmol/L but less than 7.0mmol/L and 2 hours after the sugar load blood glucose is less than 7.8mmol/L, suggesting that impaired fasting blood glucose. When fasting blood glucose is less than 7.0 mmol/L but 2-hour post glycemic load blood glucose is greater than or equal to 7.8 mmol/L and less than 11.1 mmol/L, it suggests impaired glucose tolerance. And, the normal range of fasting blood glucose is 3.9-6.1mmol/L, and the normal range of two-hour postprandial blood glucose should be less than 7.8mmol/L. Therefore, whether it is fasting blood glucose or two-hour postprandial blood glucose, 5.6mmol/L is within the normal range and does not belong to prediabetes. In case of abnormal blood glucose values it is recommended to visit the hospital.