I am still confused. If I accept the premise that we shouldn't...

I am still confused.

If I accept the premise that we shouldn't eat any blood, that is fine by me, because I don't think I do. For example I would not eat black pudding, it's disgusting.

But what does this have to do with using blood donated from another living human, to save someone's life?

I see nothing in the Bible that would prohibit this. Saving life is surely a noble deed?