You are here

How long should someone fast before a colonoscopy?


Ask anyone who has undergone a colonoscopy and they’ll likely tell you, “The procedure is piece of cake. The worst part is the preparation.”

Patients typically forego solid foods and consume only clear-liquids while taking laxatives the day before their procedure.

However, new research suggests that the process of preparing for a colonoscopy may not have to be endured on an empty stomach. The study found that patients who ate small amounts of low-fiber foods that move quickly through the bowels – such as yogurt, ice cream and macaroni and cheese – were happier on prep day and didn't suffer any negative effects during their exam.

In fact, eating these foods may stimulate more bowel movements, resulting in a cleaner colon at exam time, researchers say. The thought is that more people will have the procedure if the preparation is more tolerable.

Ransom Kilgore III, MD, a gastroenterologist at Ascension Medical Group Via Christi on Murdock, has reservations about the study’s findings. 

“The concern,” he says, “Is that foods and liquids that are not clear will not be excreted readily enough if consumed at the time of the prep. This can conceal lesions or other problems that need to be seen.”

The gastrointestinal system varies so much from patient to patient that it’s not clear how quickly the bowel contents will clear, he says. Shortening the duration of cleansing to make the process more comfortable may be a viable option for some, he adds. Patients should talk to their physician before changing their colonoscopy prep.

The American Cancer Society estimates that more than 134,000 cases of colorectal cancer will be diagnosed in the United States this year. But while colonoscopy screening is recommended at age 50 for most adults (and even earlier for those at high risk), many don't undergo the procedure.

“The procedure can be a lifesaver,” Dr. Kilgore says. “It’s my hope that people will put their health before the minimal hunger pangs they may have during the relatively short prep time.”