Whether a blood test requires fasting or not should be determined by the test item and its purpose, and cannot be generalized. Some tests may require fasting because they may be affected by eating or drinking. For the tests that have no effect, no fasting is required. 1, fasting blood draw 1, lipid testing: dietary conditions have a greater impact on the indicators examined, such as eating a large amount of fat the day before, may produce celiac blood, thus affecting the value of the blood lipid examination; 2, blood glucose testing: usually blood glucose testing will be fasting blood glucose test, requiring patients to fasting to understand the insulin situation, to avoid elevated blood glucose due to eating, affecting the judgment; 3, liver and kidney function tests. The liver function test is mainly to understand the indexes of glutamic aminotransferase, glutamic oxalacetic aminotransferase, glutamyl transpeptidase, albumin and so on. And kidney function test is mainly to test uric acid, urine creatinine and other indicators. Usually need to fasting examination, especially the liver function blood test. 1. Blood test: It is mainly to understand the situation of red blood cells, white blood cells, platelets and hemoglobin and other indicators. The normal diet does not have a significant impact on the test results; 2, blood HCG test: mainly for the determination of the HCG content in the blood, and is not affected by the sugar, fat and other substances eaten, usually without fasting; 3, hepatitis B five: because the index of the test is specific, only depends on the body’s antigen antibody situation, so eating does not affect the index, so no need to Fasting is not necessary, but if the hepatitis B tests are performed at the same time as other tests, fasting should be considered at your discretion. In addition, the fasting time should usually be more than 8 hours. If the blood test is performed in the morning, the patient can choose to fast after 10 pm the night before and eat normally for dinner, paying attention to a reasonable diet and a light diet to avoid excessive intake. After waking up in the morning or when there is a certain amount of time before the blood is drawn, drinking a small amount of water usually does not have a large impact on the test results, so patients do not need to worry too much, but they should not overdo it. In addition, the longer the fasting time, the better. If the fasting time is long, the hormones in the body will change, which will also affect the results of the blood draw. Before the test, the doctor will usually inform the patient whether the blood test requires fasting, or the patient can ask himself or herself to prepare in advance so as not to delay the test. For items that require fasting, prepare your own water in advance to avoid hypoglycemia while waiting.