Links:
Is blood donation permissible in Islam? (website)
Can we donate blood to both Muslims & Non Muslims & Can we accept money in return?
Answer:
Another concern is that, even if your niyyat to donate blood is good, but if the blood that you donated is transfused to a bad man and caused him to be well and continue doing bad things, then your deed of donating blood is counted as haram.
…………………………………………..
It is a good deed even if a non Muslim benefits from it. No one of the donors will be sinful for that.