Nervous about getting a colonoscopy? The prep is the hardest part.

Jan. 3, 2023
woman drinks water as part of her colonoscopy prep.
A lot of people dread getting a colonoscopy. Drinking a lot of water or Gatorade is all part of the prep for a colonoscopy. The actual procedure takes fewer than 30 minutes – and it could save your life. Photo: Getty Images

Colon cancer screenings save lives, but many people are nervous about getting colonoscopies.

Some wonder how long a colonoscopy will take, how best to prepare for the procedure, how much time you’ll need to take off from work and how embarrassing or disruptive this important cancer screening procedure will be.

In short, a lot of people dread getting colonoscopies. But understanding how they work — including the best options for colonoscopy “preps” you take in advance — can reduce anxiety and discomfort. And the benefits of getting colon cancer screenings are invaluable. You just might save your life.

To help answer all of your questions about colon cancer screenings, we consulted with an expert.

Dr. Blake Jones is a gastroenterologist who does dozens of colonoscopies every week at UCHealth University of Colorado Hospital. Jones is also an Assistant Professor of Medicine at the University of Colorado School of Medicine on Anschutz Medical Campus in Aurora.

Why should people get colon cancer screenings?

The answer is simple: colon cancer screenings can detect colorectal cancer early and prevent unnecessary deaths.

“Colon cancer is one of the leading causes of cancer and a leading cause of cancer deaths in the U.S.,” Jones said.

At the same time, colorectal cancers also are highly preventable and treatable if detected early. In fact, if doctors detect pre-cancerous polyps during a colonoscopy, they can remove the polyps during the procedure. Then patients may not need additional treatments or another colonoscopy for several years.

In the U.S., colorectal cancers are the third most common type of cancer that afflicts both men and women. And colorectal cancers are the second deadliest type of cancer among both men and women. In terms of cancer deaths, only lung cancer kills more people in the U.S. each year than colorectal cancers. For women, breast cancer is another deadly cancer. (View cancer statistics from the American Cancer Society.)

Jones doesn’t sugarcoat the process of getting a colonoscopy.

“It’s not pleasant, but including the prep, in most cases you’re spending less than 24 hours to help prevent cancer. For the majority of people, you’ll only need to do this every seven to ten years,” he said.

Since colonoscopies became more common around 2000, colon cancer cases have been going down among older people for whom colonoscopies have been recommended.

“We’ve seen a pretty steady decline in the number of people who have or die from colon cancer since widespread screening with colonoscopy was adopted. There’s evidence that colonoscopies make a difference.”

It is important to note that, despite the overall decline, colon cancer rates have been rising among younger people. The higher number of younger people who are being diagnosed with colorectal cancers prompted federal health officials in 2021 to recommend colon cancer screenings for people starting at age 45 or younger if they have a family history. We’ll provide more details about age recommendations for colonoscopies below.

How long does a colonoscopy take?

 The actual procedure is quick: usually about 30 minutes or less, Jones said.

Typically, people prepare for a colonoscopy in their homes the day or the night before. The preparation or prep — which involves drinking a lot of water or Gatorade mixed with laxatives or taking new FDA-approved pills — can take several hours, and it’s necessary to be close to a bathroom. That’s because you’ll be peeing and pooping out all the waste from your body, so you’ll have a clean, empty colon. We’ll provide more information below about various prep methods.

What does the doctor do during a colonoscopy?

“It’s an exam in which we look at the colon using a camera,” Jones said.

The doctor inserts a scope into the patient’s rectum. At UCHealth facilities, a patient is fully sedated prior to the start of the procedure and wakes up after it is over and usually doesn’t remember any of the procedure. For nearly everyone, the actual colonoscopy is painless and relatively quick. You arrive at a hospital or surgery center. Nurses give you an IV. An anesthetist puts you to sleep, then the doctor does a colonoscopy. You wake up, and you’re done.

“For most people, we don’t find any signs of cancer,” Jones said. “Sometimes we find pre-cancerous lesions called polyps and we remove them. It’s rare to find cancer. If we do, the idea of screening is to find it at a very early stage which increases your chances of being easily cured.”

Does a colonoscopy hurt?

For people who are fully anesthetized, there is typically no pain during or after a colonoscopy. Aside from not being able to drive themselves home from the procedure, most people feel well and are able to eat and drink normally after a colonoscopy.

What are polyps and how common are they?

“Polyps are like skin tags that form on the lining of the colon,” Jones said. “Some of them are pre-cancerous, which means that over a period of several years, they could become cancerous. So, when we find polyps during a colonoscopy, we can easily remove the vast majority of them. That’s how we prevent colon cancer through colonoscopy.”

Polyps are common and they can be non-cancerous. About one-quarter to one-half of people without a family history of colorectal cancer may have a handful of pre-cancerous polyps during their first colonoscopy.

“If you have polyps, you might have a handful of them,” Jones said.

Are polyps a big deal?

No. Many people have polyps. If they’re non-cancerous or pre-cancerous but small, they’re not a big deal. Most polyps are less than a centimeter in size.

“For people who have one or two small pre-cancerous polyps, the risk of colorectal cancer is similar to those without any polyps. It’s low,” Jones said.

During colonoscopies, doctors will detect cancer in some patients. And, after having the cancerous cells snipped, some may need additional treatments.

For patients in which cancer is detected during colonoscopy, usually via biopsy of a suspicious area of the colon, surgery or referral to see an oncologist is usually the next step.

Or, in some patients, cancerous cells may be detected after removal of polyps, and in these cases additional treatments may be necessary.

How do doctors remove polyps?

Doctors use what’s called a snare to cut the polyps.

“It’s like a little wire lasso that you use within the scope. You put it over the polyp and just snip it at the base,” Jones said.

What are the different types of colon cancer screenings?

Colonoscopy is the most widely used type of colon cancer screening in the U.S. Colonoscopies are typically recommended every 10 years starting at age 45. (People who are at higher risk for colorectal cancers may need them more frequently.)

Other common types of screening are two stool tests, one completed annually if negative, the other every three years if negative. While going to the bathroom at home, a person captures a fecal sample, then mails the sample to a lab for testing.

Are colonoscopies better than stool-based colorectal cancer screening tests?

It’s not entirely clear yet which type of screening is better, Jones said. Large clinical trials that compare colonoscopies with stool-based screening tests are being conducted in Europe and the U.S. now. So, experts soon should have more data.

While a colonoscopy is more time consuming, the benefit is that doctors can both screen for colon cancer and pre-cancerous polyps while also treating the patient by cutting out the polyps or cancerous growths if they find them.

“Unless we encounter abnormally large or difficult polyps, we always remove them during a screening colonoscopy. A stool-based test also can detect large polyps. But if you do a stool-based test, and it’s positive, you will need a colonoscopy. It will tell you that there could be something there. A colonoscopy will tell you what it is,” Jones said.

Overall, Jones’ advice is to get screened.

“We know screening is good. We like to encourage people to get whatever screening they’re comfortable getting,” he said.

If people choose to go with a stool-based test, they should know that if they get a positive result, they’ll need to follow up with a colonoscopy.

Why do you think many people are afraid of colonoscopies or put off getting them?

Many people are embarrassed to talk about poop, rectums and a procedure in which you need to have a scope inserted via the anus.

People are uncomfortable thinking or talking about colonoscopies, even though the procedure itself isn’t uncomfortable.

“It is an invasive procedure that requires sedation or anesthesia. There can be understandable trepidation about going through a procedure like this,” Jones said.

“People also fear the preparation that is required to clean out the colon,” he said.

In order for a doctor to adequately see the colon, patients need to get rid of all waste in their system.

Are colonoscopies safe?

Yes. They are very safe.

“Colonoscopies are low-risk procedures,” Jones said. “The overall adverse event rate from a colonoscopy is less than 1%.”

Tell me more about colonoscopy preps. What are they, and what’s it like to drink the prep or take the pills? Is one type of prep better than another?

 “The prep is generally the worst part. So, you get that over with first thing, then it’s out of the way,” Jones said.

 The first thing to know is that three days before you have your colonoscopy, you need to stop eating raw vegetables along with seeds, nuts and popcorn. These foods take longer to digest.

Then, on the day before your procedure, you’ll need to stop eating solid foods. And you’ll start your prep. The prep before a colonoscopy involves either taking pills and drinking a lot of liquids or drinking laxatives mixed with water or electrolytes. Patients generally need to do the prep the afternoon or evening before their colonoscopy.

People typically feel full and bloated. It’s unpleasant to drink so much and have to go to the bathroom frequently.

The prep will cause people to have very loose stools and you may feel like you have diarrhea. You may need to go to the bathroom frequently and urgently. Because of this, it’s wise to be home and close to a bathroom when you’re taking your prep.

Here are the prep options. (Your doctor’s office will give you detailed instructions and will recommend the best prep for you.)

“Each provider will have their own preference about which prep is best,” Jones said.

  • Over-the-counter laxatives with Gatorade. If your doctor recommends this method, you’ll buy Gatorade and non-prescription laxatives like MiraLAX and Dulcolax. You might also take simethicone, also known as Gas-X to reduce gas. With this method, you’ll mix the laxatives with Gatorade. People generally consume half of the mixture the afternoon or evening before the colonoscopy and half at about 3 a.m. the morning of the procedure.
  • A prescription prep that includes laxatives and electrolytes. One brand is Golytely. It’s what’s known as a polyethylene glycol or PEG. People add water to a big jug with the laxatives and electrolytes, then they drink the liquid mixture over several hours during the afternoon and night before a colonoscopy. It produces watery bowel movements to clean out the colon. Some people complain that they have to drink so much: about four liters. And the mixture can taste bad.
  • Relatively new FDA-approved pills taken with a lot of water or Gatorade. Federal health officials approved these pills in 2021, and many doctors aren’t yet recommending this method because people may not adequately clear out their colons. Also, the pills can be more expensive than other preps — especially if they’re not covered under insurance.

Jones says that the specific type of prep isn’t as important as doing it well.

“There’s not a right or wrong answer about which prep to use. I haven’t had a lot of patients use the pill prep yet. That may be because it’s new and more expensive,” Jones said.

He generally encourages people to do the lower-volume prep like the over-the-counter option.

And taking part of the prep the evening before and part the morning of the procedure seems to produce good results.

“Regardless of which pre you’re using, splitting it seems to give you a better cleansing than doing the whole prep the night before,” he said.

How important is it to do the prep properly?

A good prep is absolutely essential to getting a good colonoscopy, Jones said.

“In addition to the skill of the provider performing the procedure, the prep is the most important thing that determines the quality and value of the colonoscopy you get,” Jones said. “If you get a colonoscopy with a poor prep, it doesn’t give you protection or cancer prevention that you need. The quality of the prep is related to the doctor’s ability to detect and remove the polyps. A poor prep is associated with a lower ability to prevent colon cancer.

“If you don’t have a good prep, it’s not worth going through the procedure,” Jones said.

How do you know if you’ve properly done the prep?

Once you’ve ingested all of the prep liquid, and you’ve gone to the bathroom multiple times, you should not have any solid poops. You’ll essentially have liquid coming out of your rectum that looks like urine.

“It should mostly be yellow and translucent,” Jones said.

Are there some logistical hurdles for colonoscopies as well? Can I drive or eat and drink after the procedure?

Yes. There are some logistical hurdles related to colonoscopies.

They include:

  • Not driving yourself home.
  • Not eating solid foods in advance of the colonoscopy and doing the prep.
  • Taking time off from work to get the colonoscopy.
  • Briefly recovering and rehydrating after the colonoscopy.

Because of anesthesia, people cannot drive after a colonoscopy, but they will be able to eat and drink normally afterwards. Because people are sedated during a colonoscopy, and it takes time for the anesthesia to wear off, patients need to have a friend or family member drive them home.

Doctors also advise people not to operate heavy machinery or use an oven or stove immediately after a colonoscopy.

Altogether, how long does colonoscopy prep, the procedure itself and recovery take?

Getting a colonoscopy involves three parts.

  1. You’ll need to spend a few hours during the afternoon or the night before a colonoscopy taking the prep and going to the bathroom multiple times.
  2. On the day of the colonoscopy, patients will complete the second half of their prep in the morning. The exact timing depends on the scheduled time of their procedure. They will then need to get to their facility early and check in. They will be anesthetized. The colonoscopy, itself, will take about 30 minutes, but a patient might be at the hospital or surgical center for 2 to 3 hours. If a patient has polyps, doctors will cut them out. They then get sent to a lab so doctors can determine if they are pre-cancerous. Again, the procedure, itself, is usually painless and quick. Most people don’t remember anything about the colonoscopy.
  3. This part is usually quite easy too. Some patients will be a little loopy or sleepy after the procedure. But the anesthesia typically wears off quickly. Within an hour or two after a colonoscopy, most people feel normal and hungry.

“For most people there’s minimal recovery,” Jones said. “You wake up. You feel fine. And you can start eating.”

Are there any restrictions on eating or drinking after a colonoscopy?

No. Most patients are hungry and thirsty after a colonoscopy, and typically, it’s fine for them to eat and drink whatever they want once they are awake enough to safely swallow. Some people can be dehydrated after going to the bathroom so much the previous day and night. So, it’s wise to drink a lot of water.

Can I eat before a colonoscopy?

No. Patients can’t eat solid foods during the afternoon or night before a colonoscopy. It can be hard to skip meals and stick to a liquid diet. But the quality of your colonoscopy depends on doing a good job with the prep. So, it’s worth it. Many people arrive for their procedures very hungry.

Are colonoscopies covered under health insurance plans?

Yes. Colonoscopies are considered essential preventive screenings, and all health insurance plans should cover the cost of colonoscopies.

At what age should people get start getting screened for colorectal cancers?

Until 2021, colonoscopies were recommended starting at age 50.

Because cases of colon cancer are on the rise among younger people, the new recommended age to start screenings is age 45 (or younger in people with a family history of colorectal cancer).

Everyone ages 45 and older should get them regularly. And the U.S. Centers for Disease Control and Prevention (CDC) recommends that anyone who has a history of colon cancer or even high risk pre-cancerous polyps in their family should get screened by age 40, or 10 years younger than the age when their family member was diagnosed. Learn more about CDC recommendations related to colon cancer screenings.

What are the symptoms of colorectal cancer?

Pain in the abdomen or bloating can be signs of colon cancer. Symptoms can also include blood in the stools, rectal bleeding, changes in bowel movements like constipation or diarrhea and unexplained weight loss.

People with concerning symptoms should check with their doctor. Younger people with colon cancer often have symptoms that get ignored or misdiagnosed. Delays in treatment can be dangerous.

According to the Colorectal Cancer Alliance:

  • By 2030, researchers expect colon cancer to be the No. 1 cause of death among people ages 20 to 49.
  • People of color are at especially high risk. African Americans have the highest rates of getting colon cancer and dying from it. Colorectal cancer deaths are 40% higher in the U.S. for African Americans than for people of other races.

Read about a young woman who fought to get help after she had strange digestive symptoms.

Why are colon cancer rates rising for younger people?

Researchers still are trying to figure out why colon cancer rates are on the rise among younger people. Diets that include a lot of processed foods may be partially to blame. But the jury is still out.

“There are theories about diet, increasing rates of obesity and sedentary lifestyles, but we don’t know the cause,” Jones said.

He recommends avoiding unhealthy habits like a poor diet, a sedentary lifestyle, obesity, tobacco use and heavy alcohol consumption.

“These are all of the same things you do to maintain your general health. They will keep your other organs as well as your colon healthy.”

About the author

Katie Kerwin McCrimmon is a proud Coloradan. She attended Colorado College thanks to a merit scholarship from the Boettcher Foundation and worked as a park ranger in Rocky Mountain National Park during summers in college.

Katie is a dedicated storyteller who loves getting to know UCHealth patients and providers and sharing their inspiring stories.

Katie spent years working as an award-winning journalist at the Rocky Mountain News and at an online health policy news site before joining UCHealth in 2017.

Katie and her husband, Cyrus — a Pulitzer Prize-winning photographer — have three adult children and love spending time in the Colorado mountains and traveling around the world.