You can sleep after doing bowel prep and drinking the laxative, except that for people who do bowel prep at night there may be a disruption to their sleep. However, it takes about two hours for the laxative to work, so don’t be nervous. Generally, you should drink the laxative at 8-9 pm, excrete for about two hours, and then go to sleep at about 11 pm. Of course, there are some individual differences, some people may have a slower response to laxatives and may need to excrete for about 3-4 hours, but in most cases you can have a normal night’s sleep by 11 o’clock. If you are concerned about sleeping at night, you can also consult with your doctor or the endoscopy center’s medical staff to change the time you drink laxatives to the morning, or you can consult with your specialist in person.