An adult male has around 5 liters of blood, when you donate blood they're withdrawing at most around 500 ml, so 10%. There's a huge difference in the health eff

An adult male has around 5 liters of blood, when you donate blood they're withdrawing at most around 500 ml, so 10%. There's a huge difference in the health effects of losing 10% and 40% of your blood.