I was in terrible pain the other day near the start of my shift. It kept getting worse so I asked a colleague to tell my boss I needed to leave after finishing my current table, which was in about 10 minutes.
My boss re-arranged things to cover for me. I passed by him on the way out and he said “not feeling well eh?” I said “yeah I need to go.” He said “OK” and I walked out.
When I came back in 2 days later he asked if I was feeling better and I said “So far so good.”
That's it. End of story. Hooray for union shops!