Free tool · No sign-up · Reviewed by an anesthesiologist
Colonoscopy prep timing calculator
Enter your appointment arrival time and prep type to get a clear, hour-by-hour schedule — when to switch to clear liquids, when to take each dose, and when to stop everything.
Frequently asked questions
When do I start my colonoscopy prep for a morning appointment?
With split-dose prep (now recommended), you take the first half the evening before — often around 6 PM — and the second half the morning of, starting about 5 hours before your arrival time and finishing at least 2 hours before. For an early-morning colonoscopy that can mean waking around 3–4 AM for the second dose. Always follow the exact times printed on your specific prep kit.
Does the prep drink count as a clear liquid?
Yes — the prep solution and the clear fluids you drink with it count as clear liquids. But like all clear liquids before sedation, you must finish them at least 2 hours before your arrival time, then have nothing by mouth.
When do I have to stop drinking before a colonoscopy?
Stop all clear liquids — including water and the prep — about 2 hours before your hospital arrival time, unless your team tells you otherwise. This calculator shows your exact stop time.
Can I drink water during colonoscopy prep?
Yes, clear fluids like water, clear juice, black coffee or tea (no milk) help you stay hydrated and improve the prep — up until the 2-hour-before-arrival cut-off. Avoid anything red or purple.