There is usually no need to fast for routine blood tests. The indicators of routine blood tests mainly include the number of red blood cells, the concentration of hemoglobin, the number of white blood cells and the classification of white blood cells, etc. Generally speaking, the indicators of routine blood tests are not affected by diet. If the blood test is done alone, fasting is not required, and normal diet is sufficient before the test. If there are other tests in addition to routine blood tests, such as liver function, blood lipids, blood glucose and other indicators that are more affected by diet, fasting is required to avoid dietary interference with the test results. Before the routine blood test, you need to avoid strenuous exercise, emotional tension, and avoid measuring in an environment with too high or too low temperature. If abnormalities are found in the blood tests, further tests can be conducted as prescribed by the doctor and treatment can be provided according to the doctor’s instructions.