In a seemingly previous life, I spoke to a doctor at our hospital about blood. She said that the hospital respected the decisions of adults to do what they want....but that if the person says no blood, they don't even bring it in the room. And then she said "but be absolutely certain. We can keep it as a last resort, but many times we find that people change their minds, and then leave us scrambling to try to find what we need. Remember, your medical decisions are PRIVATE."
So yeah......a lot of JW's take blood.