My GI uses mag cit for prep as follows: Fast all day on the day prior to the scope. In the afternoon take 4 Dulcolax tablets. Drink the first bottle of magnesium citrate that evening and the second early the next morning. I get the lime flavored, which is really not bad at all, and of course the total volume is nothing comparied to the giant Golytely jug. This prep has always worked well for me. And yes, you should drink the whole bottle. It's not weight but length that matters and your intestinal tract is probably the same length as mine.