Do You Have to Follow a Clear Liquid Diet Before a Colonoscopy?

Key TakeawaysMost doctors recommend a clear liquid diet before colonoscopy.Research shows that a low-residue diet that is low in fiber might just be as effective as a clear liquid diet.However, a low-residue diet might sound more complicated for patients, and it could potentially affect bowel preparation if not followed strictly.When it’s time for acolonoscopy, your doctor might ask you to follow a clear liquid diet the day before the procedure. If avoiding solid foods seems challenging, you might wonder why this is necessary.A colonoscopy is a medical procedure used to check the colon—also called the large bowel or large intestine—for signs of cancer. A tube with a tiny camera is inserted into the anus and travels through the rectum and colon so the healthcare provider can look for tissue growths called polyps.“Visualization during a colonoscopy is key. We’re looking for polyps of varying sizes and shapes. Some polyps are flat. Being able to visually see the entire colon behind all the folds—a 360-degree view as much as possible—is important because we don’t want to miss anything during colonoscopy,”Jennifer Phan, MD, a gastroenterologist at Keck Medicine of USC, told Verywell.Phan said that a clear liquid diet would help make sure the colon is as clean as possible at the time of colonoscopy. This means only consuming clear broth, clear drinks like water and apple juice, popsicles, and Jell-O.A low-residue diet might be as effective as a clear liquid diet for colonoscopy bowel preparation, research shows.This diet includes white bread, pasta, meat, fish, eggs, certain soft-cooked vegetables, fruit without peels and seeds, and a small amount of dairy products.Rajesh N. Keswani, MD, MS, an associate professor of gastroenterology at Northwestern University Feinberg School of Medicine, told Verywell that the key is to “avoid foods that have residue,” which means foods that are hard to digest.Why Is a Clear Liquid Diet Still the Standard for Colonoscopy?People seem to tolerate a low-residue diet better than a clear liquid diet, but many healthcare providers don’t recommend this option to patients.“It is difficult to explain what a low-residue diet is sometimes. Patients will start to eat high-residue foods the day before and then really impact the bowel preparation. So, to keep the preparation simple, many people still use [a] clear liquid diet,” Keswani said.High-residue foods, like seeds, nuts, milk, whole grain breads, raw fruits and vegetables, and high-fat foods, can stick around the colon, making it harder to conduct the colonoscopy.“We see watermelon seeds all the time,” Phan said.If the bowels contain seeds, corn, or other pieces of undigested food, the provider might recommend redoing the colonoscopy.“Typically, we would have to bring a patient back either within six months or twelve months, depending on how little of the surface area we actually got to see,” Phan said.Clear liquid diets are not perfect, especially for people with diabetes, since this diet will make it harder to control blood glucose levels.Phan said there’s evidence to support recommending a low-residue diet for certain populations, especially if they didn’t tolerate a clear liquid diet in the past. However, she still recommends a clear liquid diet for most people before a colonoscopy.“We don’t have that many studies looking at polyp detection rates in clear diet versus low-residue diet,” Phan said. “Polyp detection rate is really key when trying to prevent colon cancer.”What This Means For YouMost providers still recommend a clear liquid diet, but consider speaking with a provider about your options. Some providers let patients follow a low-residue diet, especially if you have certain underlying health conditions.

Key TakeawaysMost doctors recommend a clear liquid diet before colonoscopy.Research shows that a low-residue diet that is low in fiber might just be as effective as a clear liquid diet.However, a low-residue diet might sound more complicated for patients, and it could potentially affect bowel preparation if not followed strictly.

Key Takeaways

Most doctors recommend a clear liquid diet before colonoscopy.Research shows that a low-residue diet that is low in fiber might just be as effective as a clear liquid diet.However, a low-residue diet might sound more complicated for patients, and it could potentially affect bowel preparation if not followed strictly.

When it’s time for acolonoscopy, your doctor might ask you to follow a clear liquid diet the day before the procedure. If avoiding solid foods seems challenging, you might wonder why this is necessary.

A colonoscopy is a medical procedure used to check the colon—also called the large bowel or large intestine—for signs of cancer. A tube with a tiny camera is inserted into the anus and travels through the rectum and colon so the healthcare provider can look for tissue growths called polyps.“Visualization during a colonoscopy is key. We’re looking for polyps of varying sizes and shapes. Some polyps are flat. Being able to visually see the entire colon behind all the folds—a 360-degree view as much as possible—is important because we don’t want to miss anything during colonoscopy,”Jennifer Phan, MD, a gastroenterologist at Keck Medicine of USC, told Verywell.

Phan said that a clear liquid diet would help make sure the colon is as clean as possible at the time of colonoscopy. This means only consuming clear broth, clear drinks like water and apple juice, popsicles, and Jell-O.

A low-residue diet might be as effective as a clear liquid diet for colonoscopy bowel preparation, research shows.This diet includes white bread, pasta, meat, fish, eggs, certain soft-cooked vegetables, fruit without peels and seeds, and a small amount of dairy products.

Rajesh N. Keswani, MD, MS, an associate professor of gastroenterology at Northwestern University Feinberg School of Medicine, told Verywell that the key is to “avoid foods that have residue,” which means foods that are hard to digest.

Why Is a Clear Liquid Diet Still the Standard for Colonoscopy?

People seem to tolerate a low-residue diet better than a clear liquid diet, but many healthcare providers don’t recommend this option to patients.

“It is difficult to explain what a low-residue diet is sometimes. Patients will start to eat high-residue foods the day before and then really impact the bowel preparation. So, to keep the preparation simple, many people still use [a] clear liquid diet,” Keswani said.

High-residue foods, like seeds, nuts, milk, whole grain breads, raw fruits and vegetables, and high-fat foods, can stick around the colon, making it harder to conduct the colonoscopy.

“We see watermelon seeds all the time,” Phan said.

If the bowels contain seeds, corn, or other pieces of undigested food, the provider might recommend redoing the colonoscopy.

“Typically, we would have to bring a patient back either within six months or twelve months, depending on how little of the surface area we actually got to see,” Phan said.

Clear liquid diets are not perfect, especially for people with diabetes, since this diet will make it harder to control blood glucose levels.Phan said there’s evidence to support recommending a low-residue diet for certain populations, especially if they didn’t tolerate a clear liquid diet in the past. However, she still recommends a clear liquid diet for most people before a colonoscopy.

“We don’t have that many studies looking at polyp detection rates in clear diet versus low-residue diet,” Phan said. “Polyp detection rate is really key when trying to prevent colon cancer.”

What This Means For YouMost providers still recommend a clear liquid diet, but consider speaking with a provider about your options. Some providers let patients follow a low-residue diet, especially if you have certain underlying health conditions.

What This Means For You

Most providers still recommend a clear liquid diet, but consider speaking with a provider about your options. Some providers let patients follow a low-residue diet, especially if you have certain underlying health conditions.

5 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Institute of Diabetes and Digestive and Kidney Diseases.Colonoscopy.Zhang X, Wu Q, Wei M, et al.Low-residual diet versus clear-liquid diet for bowel preparation before colonoscopy: meta-analysis and trial sequential analysis of randomized controlled trials.Gastrointest Endosc. 2020;92(3):508-518.e3. doi:10.1016/j.gie.2020.04.069GI Society.Low residue diet.Wu R, Ji W ya, Yang C, Zhan Q.A systematic review and meta-analysis of low-residue diet versus clear liquid diet: which is better for bowel preparation before colonoscopy?.Gastroenterol Nurs. 2021;44(5):341-352. doi:10.1097/SGA.0000000000000554UCLA Health.Diabetes colonoscopy preparation.

5 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Institute of Diabetes and Digestive and Kidney Diseases.Colonoscopy.Zhang X, Wu Q, Wei M, et al.Low-residual diet versus clear-liquid diet for bowel preparation before colonoscopy: meta-analysis and trial sequential analysis of randomized controlled trials.Gastrointest Endosc. 2020;92(3):508-518.e3. doi:10.1016/j.gie.2020.04.069GI Society.Low residue diet.Wu R, Ji W ya, Yang C, Zhan Q.A systematic review and meta-analysis of low-residue diet versus clear liquid diet: which is better for bowel preparation before colonoscopy?.Gastroenterol Nurs. 2021;44(5):341-352. doi:10.1097/SGA.0000000000000554UCLA Health.Diabetes colonoscopy preparation.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

National Institute of Diabetes and Digestive and Kidney Diseases.Colonoscopy.Zhang X, Wu Q, Wei M, et al.Low-residual diet versus clear-liquid diet for bowel preparation before colonoscopy: meta-analysis and trial sequential analysis of randomized controlled trials.Gastrointest Endosc. 2020;92(3):508-518.e3. doi:10.1016/j.gie.2020.04.069GI Society.Low residue diet.Wu R, Ji W ya, Yang C, Zhan Q.A systematic review and meta-analysis of low-residue diet versus clear liquid diet: which is better for bowel preparation before colonoscopy?.Gastroenterol Nurs. 2021;44(5):341-352. doi:10.1097/SGA.0000000000000554UCLA Health.Diabetes colonoscopy preparation.

National Institute of Diabetes and Digestive and Kidney Diseases.Colonoscopy.

Zhang X, Wu Q, Wei M, et al.Low-residual diet versus clear-liquid diet for bowel preparation before colonoscopy: meta-analysis and trial sequential analysis of randomized controlled trials.Gastrointest Endosc. 2020;92(3):508-518.e3. doi:10.1016/j.gie.2020.04.069

GI Society.Low residue diet.

Wu R, Ji W ya, Yang C, Zhan Q.A systematic review and meta-analysis of low-residue diet versus clear liquid diet: which is better for bowel preparation before colonoscopy?.Gastroenterol Nurs. 2021;44(5):341-352. doi:10.1097/SGA.0000000000000554

UCLA Health.Diabetes colonoscopy preparation.

Meet Our Medical Expert Board

Share Feedback

Was this page helpful?Thanks for your feedback!What is your feedback?OtherHelpfulReport an ErrorSubmit

Was this page helpful?

Thanks for your feedback!

What is your feedback?OtherHelpfulReport an ErrorSubmit

What is your feedback?