Fainting after a blood test is caused by your body overreacting to some triggers, such as the sight of blood or extreme emotional distress.
If you’re wondering why you fainted following a blood test, don’t panic! You’re not the only one. Although it might embarrass you a little, it is not too dangerous on its own.
A blood test is not a pleasant experience, and it frequently results in some level of anxiety that puts your body in an alert state. Particularly in adolescents and young adults, the perception of an unknown threat often sets off an acute stress response that prepares the body for either fighting or fleeing. This is why, prior to a blood test, you may feel your heart beating faster, your breathing becoming heavier, and your hands beginning to sweat.
In an effort to regain balance, the body reacts by reducing blood pressure and slowing the heart rate. Even though this is a normal process that occurs in everyone, in certain individuals the nervous system’s reaction is exaggerated, causing the blood pressure and heart rate to fall dramatically. Low blood pressure in the blood vessels causes blood to pool in the legs, which reduces blood flow to the brain. At this point, the body’s response is to make you feel faint so that you can quickly lie down and re-establish blood flow to your brain.
What should I do if I feel lightheaded during a blood test?
Before you pass out, you will experience warning signals. You might feel weakness, dizziness, sweating, or rapid breathing. Your skin may become pale, hot, sweaty, and nauseated, and you may begin to have tunnel vision.
If you feel like this, inform the phlebotomist straight away and ask him/her to lie you down. Lying down is the easiest technique to prevent fainting, as it allows the blood to reach the brain more easily and you are less likely to lose consciousness.
