Hello, I am preparing for colonoscopy tomorow at 10 AM. Liquid diet all day, then, as instructed, I drank about 12.5 ounces of Magnesium Citrate, four hours ago. Nothing happened so far. Should I worry about my colon preparation for tomorrow s procedure? I have been instructed also to drink another 12.5 ounces at 4 AM. When should I expect to see the effects of Magnesium Citrate? Thank you.