Fasting blood glucose is blood taken after an overnight fast and before breakfast. Generally, to draw fasting blood glucose, you need to fast for more than 8 hours, and snacks and fruits should not be consumed again. If blood is drawn at 8:00 a.m. the next morning, no further food may be consumed after 12:00 p.m. the night before. If the patient is concerned about the effect on the results, he or she can extend the fasting time a little longer, such as 10 hours of fasting. In fact, there is not much restriction on drinking water, and you can drink small amounts of cool, lukewarm water, as long as you do not add sugary sugar to the water. The previous day’s diet should be kept normal, with a certain amount of carbohydrates, around 100g. If deliberately reduced, it will have an effect on the measurement of blood glucose values. In addition, the previous day’s diet should be light, about the same as usual, without large fish and meat, drinking alcohol, so as not to have an impact on the following day’s blood sugar. Patients should also refrain from strenuous exercise and emotional fluctuations the day before the fasting blood glucose draw, because emotional fluctuations and strenuous exercise can cause excessive secretion of glucagon. Because many patients with blood sugar problems also have problems with insulin, insulin can be tested along with the blood sugar test.