For healthy citizens, it is generally appropriate to donate between 200-400ml of blood at a time. Donating about 200ml of blood at a time has no effect on your health because the body’s blood production function is very strong. 200ml of blood is donated at a time and basically soon the body will compensate for the increase and have new blood components to replenish up. However, the best advice is to estimate according to one’s own weight, because the amount of blood in one’s body is proportional to one’s own weight, because the total amount of one’s own blood accounts for about 7-8% of one’s own weight. For a healthy adult weighing about 70 kg, if he donates 400 ml of blood at one time, the total amount of blood donated is less than 1/12 of his whole body blood volume, which should not have any effect on his body. For women with a body weight of about 50kg, a blood donation of about 200ml is more suitable and will not cause any obvious discomfort after donation. Therefore, it is best to estimate how much blood is appropriate to donate at one time according to your own weight.