It is recommended to fast for more than eight hours for liver function tests and try not to eat breakfast. Fasting for eight hours means not to eat eight hours before the test. In addition, do not eat high-protein, high-fat or stimulating foods the night before to avoid affecting the test results the next day and causing an elevation in enzymes such as glutathione and glutamic acid aminotransferase. To avoid false elevation, it is recommended to fast for more than eight hours when checking liver function. For routine biochemical tests, fasting in the morning is generally recommended unless there are special requirements. Some items do not strictly require fasting and require blood collection according to the clinician’s instructions.