Blood composition is influenced by diet, mood and muscle activity. Meals can increase blood indicators such as glucose, triglycerides, urea nitrogen, uric acid, insulin, bilirubin, alkaline phosphatase, and lactate; they can also decrease indicators such as total serum protein, albumin, hemoglobin, hemoglobin, hematocrit, free fatty acids, and inorganic phosphorus, and many of the above indicators are health evaluation indicators that have important initial screening significance in our health checkups. Therefore, health checkups are usually performed in the morning, first of all during fasting when blood is collected from a vein, otherwise, if blood is collected after a meal, it is difficult to determine whether the abnormal test indicators are due to the impact of the meal or the body itself has undergone pathological changes. Therefore, we usually ask for blood collection on an empty stomach during the health checkup.