There is no need to fast for the Hepatitis B half-pair test, but if the liver function test is done at the same time, fasting is required. Nowadays, before many blood sampling programs are conducted, they will be told that fasting is required, this is because in the fasting state, the body is in a state of basal metabolism, and the influence of diet and other factors can be excluded. Hepatitis B two halves itself has little to do with one’s diet and so on, so the test for hepatitis B two halves does not require fasting. However, if the patient wants to check the liver function at the same time, then it is necessary to ask for fasting. Because drinking a lot of water before the test will dilute the blood and lead to errors in some test values, but there is no harm in drinking a small amount of water (50-100 ml) in the morning of the day of the blood draw or in the evening before the day of the blood draw, as long as you are not pouring water vigorously or drinking a few hundred ml at a time, it will not affect the results of the test.