Re: I have several blood donor cards.
Are you sure this is American?
When you need life-saving measures, you get life-saving measures. You don't, as Dave said, not get needed blood because you yourself are not a donor.
I have a blood donor card, which simply facilitates the process of giving blood. They already know who I am, where I live, etc.
Blood donation is of course entirely voluntary.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.