Ill be starting my liquid preop diet in the next few weeks. I decided to give up caffeine/carbonation first so it wasn't all at once. Yesterday was my first full day without caffeine..I felt tired and cranky at work and then at the end of my work day had the worst headache ever..came home felt like I had the flu or was withdrawing from heroin..body aches, sweating, shivering..basically slept from 6 pm to 5 this morning. Now I feel fine. Is it possible the detox took 24 hours and now it's over? I've always heard stories of caffeine taking a week to get over. Any insight?