Do you really have to drink the entire 2 liters of Half Lytely before a colonoscopy?

Yes ! they didn't tell you to drink it just to be mean. They want your colon to be completely cleaned out so that even a slight sigh of anything remaining won't be mistaken for a polyp or cancer. Then you would have to go in for diagnostic surgery.Plus believe me the Dr who does that surgery will be glad there is nothing yucky in your colon that he has to deal with or byp to get the results he wants . Good luck and believe me , the procedure is a painless and over quick. they gave me some drugs , and I woke up in recovery. Not nearly as bad as I imagined.