Excuse me, Professor, I have a problem and need to leave class early.
Why do you have to leave early?
I am not feeling well.
Could you make it up by attending my other section this week?
Yes, it's all taken care of.
Are you leaving right away or can you stay for a few more minutes?
I can stay a few more minutes.
OK, but please make sure that you get all of your make-up work completed.
Thanks, Professor. I've got it covered!
Go do what you have to do, but make sure it doesn't happen again.