Fasting blood glucose can reflect the function of pancreatic islets and is a common indicator in clinical practice, but some patients think that fasting means starving, and the longer they are hungry, the more accurate the indicator is; some patients are afraid that the indicator will be high, so they do not eat or eat less the night before the blood draw, or they intentionally delay until after 10:00 to draw blood. This is not true. In daily life, many patients have many misunderstandings about “fasting”, fasting blood sugar is not equal to “starving” blood sugar, and there is no need to deliberately starve for a long time before measuring fasting blood sugar. The human body has a strong self-regulation function, when the body is in a state of hunger, the indicators of the body’s functions will change, so the collected blood samples will be distorted, and the results may look “normal” from the figures, but behind the scenes may conceal the real condition of the patient. A large number of clinical practice has proved that when diabetic patients fast for too long, the blood glucose test results will appear in two ways: one is lower than the actual index, which is easy to be mistaken for good blood glucose control; the other is that some diabetic patients are extremely sensitive to their own blood glucose regulation, and when they are hungry for a long time, they will immediately mobilize the glycogen in their bodies for urgent needs, resulting in blood glucose levels that are much higher than usual, both of which will mislead doctors to make incorrect diagnosis and misdiagnosis. Both of these illusions can mislead doctors to make incorrect diagnosis and misdiagnosis, and some of them may lead to deterioration of the disease. It is also worth noting that some diabetic patients may suffer from hypoglycemia or even fainting if they are hungry for too long, which may endanger their lives. The best time to test fasting blood glucose is between 8-12 hours after meals. The night before the blood draw, you should keep your usual habits and eat normally, meals should be light, don’t drink alcohol, don’t drink coffee or strong tea after meals, don’t eat after 10 o’clock, and ensure sufficient sleep. The next morning after getting up do not eat anything, drink little or no water, and at the same time avoid getting too emotional and doing too strenuous activities. The best time to draw blood is between 6-8 am, so that the blood specimen can reflect the real situation of the patient.