Getting ready for a colonoscopy

Why the prep matters

A colonoscopy uses a thin, flexible camera to look inside your colon (large bowel). The doctor can only see clearly if the colon is empty and clean. If it is not, small polyps or areas of inflammation can be missed, and you may need to repeat the test.

One week before: check your medicines

Call your clinic or the doctor doing the test if you take any of these. Do not stop them on your own.

• Blood thinners, such as warfarin, apixaban (Eliquis), rivaroxaban (Xarelto), dabigatran, clopidogrel (Plavix) or ticagrelor. Some are kept going and some are paused for a few days. It depends on the medicine and why you take it. Low-dose aspirin for your heart is usually not stopped.
• Diabetes medicines, including insulin. You will eat less during the prep, so your doses may need to change. Check your blood sugar more often.
• GLP-1 medicines, such as semaglutide (Ozempic, Wegovy, Rybelsus), liraglutide or tirzepatide (Mounjaro, Zepbound). These slow down the stomach. Your team may ask you to keep taking it and have only liquids for the full day before. Or they may ask you to skip a dose. Tell them if you have nausea, vomiting or bloating, or if your dose was raised recently.
• Iron pills. Many clinics ask you to stop them several days before, because iron can darken the stool and make the bowel harder to see.
• Fibre supplements, such as psyllium (Metamucil). Ask if you should stop them.

Also tell your team if you are in a flare, have a narrow spot in your bowel (stricture), have kidney or heart disease, or are pregnant. They may choose a different prep.

Keep taking your IBD medicines unless you are told otherwise.

The day before

Eat low-fibre food for breakfast and lunch. Some clinics ask you to start a low-fibre diet a few days earlier.

Then switch to clear fluids only. Your clinic will tell you when. Clear fluids are drinks you can see through. Drink plenty, to stay hydrated.

Red and purple dyes can look like blood in the bowel, so skip them.

Taking the prep: split dose

Most clinics use a split dose. You drink the prep in two parts. This cleans the bowel best.

1. The evening before

   Drink the first part, as your instructions say.

2. The morning of your test

   Drink the second part. You usually start it about 4 to 5 hours before your test time, and finish at least 2 hours before. If your test is very early, this may mean getting up in the night.

3. Before the test

   Stop all drinks when your clinic tells you, often 2 hours before the test. This makes sedation safer.

If your test is in the afternoon, your clinic may have you take all of the prep that same morning.

Tips:

• Chill the prep and drink it through a straw.
• Drink a glass of a clear fluid you like after each glass of prep.
• Stay close to a toilet. The prep often starts working within an hour or two.
• Soothe sore skin with a barrier cream or wet wipes without alcohol.
• Your clinic may add an anti-gas medicine called simethicone (Ovol). It helps clear bubbles.

Is my prep working?

By the end, your stool should be watery and clear or yellow, a bit like urine or weak tea. There should be no solid bits. A few flecks are usually fine.

If your stool is still brown and thick when you are near the end, or if you vomit the prep, call your clinic. Do not give up and do not cancel on your own. They can tell you what to do.

On the day

After the test

• Sedation can affect you for the rest of the day. For 24 hours, do not drive, use machines, drink alcohol, or make big decisions. It is best to have someone stay with you.
• Gas and bloating are common for a few hours, because air is used to open the bowel. Walking and passing gas help.
• A small amount of blood can happen if polyps were removed or biopsies were taken.
• You can usually eat soon after. Start with something light.
• Ask when you will get your results, and when to restart any medicines you paused, such as blood thinners.

If you have any of the warning signs below, get help right away.