system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do they refrigerate donated blood? Why not keep it at body temperature?

I just donated blood and it reminded me of something I've often wondered about. Why do they refrigerate donated blood? It seems like it'd make more sense to keep it at body temperature, if that's what keeps it "good" while it's still in your body. What becomes different once it's no longer in your body?
gpt
Blood in your body is active.  It is used, moved around, and its components are continuously replenished when needed.  Donated blood just stays there.

It's quite similar to why we keep vegetables in the refrigerator once they're picked up.  Out of their environment, they are not keeping themselves fresh anymore and start decaying.  They don't decay as fast when we keep them in the cold.