Do I have to fast to have my blood drawn? In outpatient clinics, we often encounter patients who request to be seen early, who are too hungry to eat because they are waiting for their blood to be drawn, and who are so dizzy and sweaty that they are at risk of fainting at any time. When the doctor takes a look at the items to be tested, he finds that eating will not affect the test results at all, so he immediately instructs the patient to hurry up and eat. So what tests need fasting? What tests will not be affected by eating? Let’s understand why fasting is necessary for blood tests! To avoid the effect of diet and other factors on some components of the blood. Because food is absorbed from the gastrointestinal tract into the bloodstream and then transported throughout the body by the blood, eating can have a significant impact on the target chemical levels to be tested in the short term. The intake of protein (such as eggs, milk, beans, lean meat, etc.) will significantly increase the liver-produced transaminases in the blood, and this indicator is a typical indicator of liver function; if the intake of purine-rich foods (such as mushrooms, seafood and other foods), the blood creatinine concentration will rise significantly, and this indicator reflects the good or bad kidney function; the intake of a large amount of sugar (such as rice, pasta), blood sugar will transiently rise, and abnormal blood glucose suggests that the subject may have diabetes. Therefore, eating can increase the concentration of certain components in the blood, which in turn affects the accuracy of the test results. Blurred observations: After eating, various particles of digested food chyme are quickly absorbed into the bloodstream, making the blood appear cloudy, often called “fatty blood”. This also makes it impossible for the examiner to see clearly. It is more relevant to the body’s state: generally early in the morning, the mood is more stable, the body is in a basal metabolic state, the test results can more truly reflect the actual situation of the patient. By fasting, I mean no more food after dinner and no breakfast the next morning, in this case the blood test is drawn, the results are better. However, there are some tests that do not require fasting, such as routine blood tests, Down screening and non-invasive DNA. There are also some hormones, which are more stable in concentration over a certain period of time and are not restricted by diet, such as blood beta-hCG, growth hormone and tumor markers for detecting early pregnancy.