Colonoscopy Prep Timeline Calculator

Colonoscopy prep involves several steps spread over multiple days, and the timing matters. Missing a window or starting too late can affect the quality of your prep — and potentially your results. This calculator takes the guesswork out of the process.

Enter your procedure date and time below, and we'll generate a personalized timeline showing you exactly when each step typically begins. Think of it as a roadmap for the days leading up to your colonoscopy.

Sample prep timeline

Procedure date

Procedure time

Prep type SuPrep GoLYTELY MiraLAX / Gatorade Clenpiq Sutab

Generate example timeline

How this calculator works

This tool uses the most common prep timing guidelines to estimate your schedule. It works backward from your procedure time to calculate when you'd typically begin each phase. Here's what goes into the calculations:

• Low-fiber diet: Most doctors recommend starting a low-fiber diet about 3 days before your procedure. This means avoiding seeds, nuts, raw vegetables, and whole grains to reduce the amount of residue in your colon.
• Clear liquids: The day before your procedure, you'll usually switch to clear liquids only — broth, clear juices (no red or purple), gelatin, tea, and water.
• First dose timing: For split-dose preps, the first dose is typically taken in the evening before your procedure, usually around 5–6 PM. Your specific prep may vary.
• Second dose timing: The second dose is usually taken 4–5 hours before your scheduled procedure time, giving the prep enough time to work while still meeting the liquid cutoff.
• Liquid cutoff: Most facilities require you to stop drinking all liquids 2 hours before your procedure for safety during sedation.

The timeline adjusts the second dose window based on your procedure time. For later procedures, the second dose may shift to early morning rather than the middle of the night.

Important notes

Every person's situation is different. This calculator is meant to give you a general sense of the prep timeline, but it cannot replace the individualized instructions your doctor provides. Here are a few things to keep in mind:

• Your doctor's instructions come first. If your paperwork says something different from what this calculator shows, follow your doctor's guidance.
• Prep types vary. Different prep solutions have different volumes, dosing schedules, and timing requirements. Some are taken as a single dose rather than a split dose.
• Medical conditions matter. If you have kidney disease, heart failure, electrolyte disorders, or other conditions, your doctor may prescribe a different prep or different timing than what's shown here.
• Medications need attention. Some medications need to be stopped or adjusted before a colonoscopy. Talk to your doctor about any prescriptions, supplements, or over-the-counter medications you take regularly.
• Afternoon procedures have different timing. If your procedure is scheduled for the afternoon, the second dose timing will be later than for a morning procedure. Your doctor should provide specific guidance.

If anything about your prep instructions is unclear, don't hesitate to call your doctor's office. They answer these questions every day and would rather clarify than have you guess.