Splitting doses: A good strategy for colonoscopy preparation?

Date Updated: 02/23/2021

Answer Section

To make bowel preparation more tolerable and improve outcomes, many doctors recommend splitting the dose of bowel preparation solution. This regimen may not be possible if your colonoscopy is scheduled for early in the morning, because you should consume the morning dose three hours before leaving home for the procedure.

If your procedure is scheduled at a time that allows you to split the dose, follow the instructions provided by your doctor. Take the recommended amount of the bowel cleansing liquid the night before the exam, and the remainder in the morning before the test. Or if your procedure is scheduled for afternoon, your doctor might recommend that you split the dose on the day of the test.

The biggest reason for poor colonoscopy preparation is people's distaste for having to drink large quantities of bowel cleansing solution. The most common colonoscopy preparation calls for drinking 1 gallon (3.8 liters) of a polyethylene glycol solution. Many people don't complete the full preparation.

Studies have shown that the split-dose approach not only is more tolerable but also does a better job of cleaning the colon. Better cleaning will lead to better results. One study found that doctors detected more benign polyps in people who prepared with split doses than in people who prepared with single doses.

Cleaning as much waste material as possible from your large intestine (colon) is crucial to a successful colonoscopy exam. Poor colonoscopy preparation can prevent your doctor from finding polyps, tumors and other problems. It also increases the length of the exam and the risk of complications. In many cases, the exam has to be redone.

Ask your doctor about split-dose preparation for your next colonoscopy.