Before the physical examination, you will always hear such instructions: “to draw blood, do not eat after 8 pm, come tomorrow morning on an empty stomach ……” So many people worry, “If I drink a sip of water in the morning, it will affect the test results? ” Or “Is it true that the longer you are hungry, the more accurate the test results will be? Fasting ≠ hunger Fasting blood can exclude the influence of diet and other factors, reflecting the real situation in the human blood. But fasting is not the same as hunger. It is because when the body is starving, the number of indicators of body functions will change, which cannot accurately reflect the real situation of the patient. How to fasting The night before the blood draw, normal diet, meals should be light, do not drink alcohol, otherwise the alcohol content in the blood, will directly lead to higher or lower results; after 8 pm should be fasting, do not drink coffee, strong tea, rest well. The next morning after getting up, do not eat breakfast, drink little or no water, do not do early exercise exercise, because strenuous exercise can make some indicators rise momentarily. Go to the hospital calmly and wait for blood collection, so that the blood specimen is a good specimen to reflect the real situation. Some patients have particularly high triglycerides, so that the serum is like milk, which affects the accuracy of the laboratory results of other lipid items. In this case, the doctor will ask them to eat a vegetarian diet for a few days and then do the fasting blood test. What tests require fasting In general, liver function, kidney function, biochemistry, lipid and blood glucose tests require blood to be drawn early in the morning on an empty stomach. Other tests that require fasting are blood sedimentation test, serum iron, transferrin, etc. Three immunoglobulin tests (IgA, IgG, IgM), three rheumatic tests (ASO, RF, CRP), and sex hormone tests are also best done with fasting blood. Finally, it should be pointed out that the blood drawn for the test is generally less than 1% of the body’s blood volume, so the impact on the human body is minimal, so the body can adjust and recover on its own after the blood is drawn, and no special supplementation is needed.