Can a next of kin authorize a family member, who is in a coma, to donate blood?

Used to be, no. At least in the US, in the state where I was. Unless a medical proxy, that specifically includes any bodily product of the incompetent or incapacitated person that can be donated without damaging said person, is in place.

What a travesty if they could just arbitrarily harvest bits of people who are unable to object.

If they could authorize blood donation, they could then authorize kidney donation.

I think that’s a state by state decision tied to the state’s laws. After I had my stroke, I wasn’t allowed to give blood because I was considered to have an unknown medical condition & I might be taking meds that could have adverse effects on the recipient. I think that they said that I had to wait 2 years & have an “all clear” from my doctor before they would accept my blood again. That might have been a donor center rule as well.

I don’t think so. I think the only donations a next of kin can authorize is after death and I don’t think blood donation is done after death. As far as I know only organ donation after death.

One exception might be parents authorizing for a minor child. That would seem to have all sorts of ethical questions (which it should) but what if it was a donation for a sibling or parent?

This is just my opinion but I think that would be creepy and not right to do. Plus someone in a coma is probably on medicines that would not be wanted in donated blood products anyway.