There is no necessary connection between blood draw and headache. Generally, when doing clinical examination, the number of milliliters of blood drawn per tube is 1-2mL, which will not affect the human blood system, blood pressure and hemodynamics, and theoretically will not cause headache in a person, and no headache has been seen clinically. If there is a headache, you need to be alert to the fact that it may be due to some other reasons, as follows: 1. Emotional tension: After the blood draw, the patient is very nervous and anxious, and the nervousness and anxiety will cause the person’s blood pressure to rise, which may lead to a headache. This time you need to relax and do some deep breathing, generally the patient headache phenomenon can be relieved. 2, have other diseases: the patient itself has high blood pressure, blood pressure fluctuations after the blood draw, high will cause headaches, migraine attacks can cause headaches, just happen to occur brain hemorrhage, etc., can also cause headaches.