I have a really funny storry about the first time I took the MCAT.
So probably 30 min before my 1:00PM exam I chugged a 16oz redbull and I am a small individual with probably the smallest bladder EVER made. Half way during PS I was just praying for the section to be over so I could use the restroom. So finally the break came and I went and came back I guess 1 min before my time was going to start. Anyway my proctor was the meanest person that worked that day and she was like you're late blah blah.. and I am not one to sit there an argue so I said okay I was in the bathroom what do you want me to do. And she said she is going to have to document that I was "late". Since it was my FIRST TIME I kind of freaked out because in all reality that sounds like a pretty bad thing .. and I assumed they would send it to AAMC and my score would be voided and the world was going to end.
So after the test I called AAMC and the guy just laughed and apologized for the horrendous experience I had, made sure to take down the center's name so it wouldn't happen again. He pretty much said any time you are "late" your section just starts on the computer and that's that. Nothing gets reported or noted down or whatever else that proctor made me believe.
Moral of the story don't chug red bull