The second is to ensure that blood donors will not have adverse reactions due to blood donation, and it is estimated that they can provide blood such as shock.
Testing blood type is the basic operation, because each recipient's physique is different. Under the action of the autoimmune system, blood of different blood types will be infused into the body, which will lead to the death of the recipient (for example, O blood can only accept O blood, and A\B\O\AB blood can also be divided into RH negative and positive). Only by testing the blood type of blood donors can we determine the blood type in advance and provide healthy and correct blood to the recipients in time, killing two birds with one stone ~
As for drinking water, there should be no problem, but it is recommended to drink sugar water to supplement the physical strength consumed during blood loss.