I'm Gonna Have A Colonoscopy At 7 Am Tomorrow. I

I'm gonna have a colonoscopy at 7 am tomorrow. I was advised not to take the one-milligram glimiperide tonight or tomorrow in the morning. I took 1 mg this morning, though. I usually take 1mg in the morning and 1mg before bedtime. I just measured my glucose level now and it is 82. For me this level is enough to make feel lightheaded. My question is - how long is the action of this medicine? I took it at 10 a.m.