Blood tests are an important part of checking for diseases and conducting health checkups. Many diseases or health checkups require blood analysis to detect them, so blood tests are very important. Blood is usually collected from a vein, and generally blood tests require fasting to test, because diet can have some effect on blood, such as measuring blood sugar, if you eat, it will have an effect on fasting blood sugar. There are also lipids, if you eat a lot of oily food before the blood is drawn, it will lead to elevated lipids and the measurement will be biased. There are also some cortisol tests that need to be taken at different times of the day depending on the biological cycle. Because of the biological cycle, it is better to have the results measured at the same time for them to be comparable. Some blood tests do not require fasting, you can eat, and eating does not have much to do with, for example, blood tests, blood coagulation and other tests have little to do with diet, so you can test after meals.