Why do people pass out when they give blood?

Question

I imagine it’s a lot of fear and anxiety but why does the body react so dramatically?

In: 21

Answer 1

When you give blood, the loss of blood causes your blood pressure to drop. Your brain needs a lot of oxygen from the blood to operate, and it’s particularly susceptible to a drop in blood pressure because it’s at the top of your body. When the brain doesn’t get enough oxygen to operate, you pass out.