Fasting for 14 hours may lead to elevated blood glucose, and hypoglycemia may also occur. There are many factors affecting the increase of blood glucose after prolonged fasting, such as physiological blood glucose increase in the early morning and rebound blood glucose increase after hypoglycemia, and it is recommended to consult a doctor in time to improve the examination. The body is affected by the biological clock, there is a circadian rhythm of hormones in the body, and the level of glucagon, cortisol and other blood sugar-raising hormones rises in the morning, which may lead to a rise in blood glucose even if you have not eaten. In addition, hypoglycemia at night may lead to stress in the body, resulting in a rebound increase in blood glucose. Therefore, if high fasting blood glucose occurs frequently, it is necessary to improve the postprandial blood glucose, glucose tolerance, glycated hemoglobin and other related tests to make a comprehensive judgment. In clinical practice, fasting blood glucose test needs to fast for 8~10 hours before checking, usually at 6-8 o’clock in the morning for fasting blood glucose measurement and other laboratory tests that require fasting, which is more accurate. Fasting for 14 hours is more likely to result in hypoglycemia, and thus a greater likelihood of rebound blood glucose elevation when measuring blood glucose. Seek medical attention for blood glucose abnormalities.