1. Ada
  2. Preparing for a Colonoscopy

Preparing for a Colonoscopy

Written by Ada’s Medical Knowledge Team

Updated on

What is a colonoscopy?

A colonoscopy involves inserting a thin, flexible tube called a colonoscope into the body through the anus to examine the colon (large intestine) and rectum. The main purpose of a colonoscopy is to investigate symptoms which may be coming from the colon and colorectal area, such as:

  • Abdominal pain
  • Constipation
  • Passing blood with bowel movements.
  • Persistent diarrhoea

During a colonoscopy it is possible to identify growths and other intestinal problems; including:

  • Non-cancerous polyps
  • Colon cancers
  • Bleeding
  • Areas of inflammation

It is necessary for the whole colon to be visible to the video camera on the end of the colonoscope, otherwise it is impossible to carry out this screening process effectively. If you are concerned about the health of yourself or a loved one, download the Ada app for a free assessment.

People are recommended to follow particular instructions in preparation for a colonoscopy, including following a specialized colonoscopy prep diet and activity plan. The purpose of this is to induce a kind of diarrhea, emptying the area to be screened of stool and other waste to ensure full visibility. This process is known as colonoscopy prep.

How to prepare for a colonoscopy: what to expect

The aim of colonoscopy prep is to ensure that the colon is empty and clean before the screening. This normally involves:

  • Following a colonoscopy prep diet. This is made up of low fiber food; this stage lasts for three to four days, with a liquid-only food intake on the final day before the colonoscopy.
  • Drinking bowel-cleaning liquids. These are medications called laxatives, which may take the form of pills or drinks, and which are taken to induce diarrhea. They will most commonly be taken the night before the screening, often with another dose on the morning of the screening. This is called a split-dose-regimen. 1 2
  • An enema before the colonoscopy. This may be given in cases where the large intestine is difficult to empty, for example due to constipation.

Good to know: People preparing for a colonoscopy experience frequent bowel movements as the preparatory medications take effect, and will need ready access to a bathroom at all times. It is for this reason that clearing one’s schedule of appointments for at least one day before the screening and staying at home are both highly recommended.

Colonoscopy prep tips: creating the optimum setup

Before starting colonoscopy prep, most people find it helpful to shop for all the supplies that they will need. In addition to the foods and liquids that will be eaten as part of the food intake plan, people preparing for a colonoscopy may wish to purchase products to soothe the skin around the anus, specifically diaper cream (to soothe the skin) and alcohol-free cleansing wipes containing aloe-vera or vitamin E.

Food planning for colonoscopy prep: what to eat and what to avoid

During colonoscopy prep, one should aim to eat a diet which is nutritious, but which does not cause large amounts of feces to form in the intestine. Three days in advance, it is important to stop taking fiber supplement products, as these help the body to produce fecal matter and would work against the colonoscopy preparations.

At this point, it is important to stop taking all other supplements and vitamins, as well as any medicines that contain iron. 3 Physicians or hospital staff will advise on whether and when to stop taking any prescription medicines that are normally used regularly, and on the use of over-the-counter anti-inflammatory medications, such as ibuprofen.

Low fiber food

Eating low-fiber food for three or four days before the procedure will help to empty the colon, because low-fiber foods are easy to digest and leave one’s system quickly.

Foods to avoid during colonoscopy prep include:

  • Fatty foods
  • Fruit with seeds or peel such as apples, berries or figs
  • High-fibre cereals such as bran flakes or granola
  • High-fibre vegetables such as corn, broccoli, cabbage, beans or peas
  • Legumes such as dried peas, lentils or split peas
  • Seeds, nuts or popcorn
  • Tough meat with gristle
  • Raw vegetables
  • Whole grains

Low-fibre food options which are suitable for colonoscopy prep include:

  • Cooked vegetables without skin or peel
  • Eggs
  • Fish
  • Fruit without skin or seeds
  • Lean meat such as chicken, turkey or veal
  • Well-cooked vegetables without skin
  • Breads and cakes made with refined white flour such as bagels, muffins or rolls
  • Pasta and rice
  • Potatoes without skin
  • Smooth peanut butter or almond butter

Avoid solids

The day before before the colonoscopy, it is recommended to avoid solid food completely. Consuming liquids only for this time period helps prevent new fecal matter from forming, entering the colon and being present during the screening, and will ensure that the colon remains empty and clean.

It is important to avoid red and purple food dyes 4 as they can discolor the lining of the colon and make it harder to see the area being examined during the colonoscopy.

Drinks and liquid foods which are suitable to eat the day before the screening include:

  • Clear broth, including chicken, beef, or vegetable
  • Clear, light-colored juices such as apple, white grape, lemonade without pulp, and white cranberry
  • Flavored water
  • Jell-O or other gelatin without fruit (taking care to avoid red and purple food colouring)
  • Popsicles without fruit or cream
  • Water
  • Soda
  • Sports drinks such as Gatorade and Propel (light colors only)
  • Tea and black coffee without any cream, milk or sweetener

Cleansing the bowel

The aim of colonoscopy prep is to pass all the fecal matter from the area to be examined during the screening, so that there is nothing left to obstruct the view of the colonoscope. To aid the process of emptying the bowel, one will be prescribed a laxative product to take as part of the colonoscopy prep. In some cases, enemas may also be prescribed.

Good to know: Many people pass clear, yellow liquid once they have finished passing waste. This yellow liquid which a person may pass is made up of digestive juices and does not indicate that the prep has been ineffective. However, if the person preparing for the colonoscopy is still passing liquid containing fecal matter, or brown, cloudy liquid, they should seek medical advice as they will need to take additional steps to clean their colorectal region before the screening can be performed.

Colonoscopy prep medications

Laxative medications help the stool to pass smoothly through the colon.

Before a colonoscopy, osmotic laxatives are most commonly prescribed. These work to empty the bowel by drawing the water from the large intestine into the stool in order to soften it, making it easier to pass. These are usually drunk dissolved in large amounts of water. Specific instructions for preparing the solution vary from brand to brand, and will found be on the packet of the product that has been prescribed.

Seek medical advice if there is any confusion about how to prepare the solution and when to take it. Because these medications work by keeping water in the bowel, it is important to drink enough liquid to stay hydrated. Drink water, or one of the recommended liquids, regularly throughout the colonoscopy prep plan.

Good to know: It is important, and not harmful, for a person preparing for a colonoscopy to drink the prep solution as planned, even if they already have diarrhea before starting to to take it. The prep solution is designed to ensure that any solid stool which may have formed higher up in the colon is passed before the scan.

How long should colonoscopy prep take to start working?

Most colonoscopy prep products start working two to three hours after they are taken, although the exact time-frame varies between medications. In some cases, if bowel movements do not begin to occur when expected, an extra dose may be needed. However, it is always advisable to follow the specific instructions that come with the product in relation to taking an extra dose and to consult with one’s medical provider in case of any doubts.

How to drink colonoscopy prep medications without throwing up

It is possible for drinking the solution to make one feel nauseous. Tips which may help a person to avoid nausea include:

  • Sipping the solution slowly
  • Taking breaks between sips
  • Using a straw
  • Cooling the liquid instead of drinking it at room temperature

If nausea is known to be a problem for the affected person in general, or has been experienced in a previous screening, anti-nausea medications may be recommended. 5

To avoid vomiting, it can also be helpful to leave longer intervals between drinks. If someone does vomit after consuming a dose of the solution during their colonoscopy prep, it is important to repeat the dose.

How to tell if colonoscopy prep has been effective: what to expect

Prep is complete when bowel movements become watery and clear. This means that the colon is empty of fecal matter and is ready to be viewed by the colonoscopy camera without obstructions. The length of time that it takes to reach this point will vary between people and will depend on factors, such as their overall gastrointestinal health, and how well the prep diet plan was followed.

Good to know: When bowel movements become clear enough to see the bottom of the toilet bowl, colonoscopy prep can be considered complete.

Seek medical attention if significant amounts of blood, or blood clots, are passed during colonoscopy prep. Colonoscopy prep may cause any hemorrhoids that are present to bleed slightly, as they might normally during a bowel movement. In all cases where bleeding appears to come from a source other than existing hemorrhoids, or is excessive, a medical opinion should be sought as soon as possible, and the bleeding should be mentioned before the procedure. 6

What to do if colonoscopy prep is not working

The purpose of colonoscopy prep is to remove all fecal matter from the bowel. If a person usually suffers from constipation or chronic constipation, they may need an extended prep period before their colonoscopy. It is helpful to discuss constipation issues with the doctor when planning a colonoscopy, so that the preparation time can be adjusted if needed.

An extended preparation period typically involves the use of enemas and doubling the colonoscopy prep time-frame. Prep will then involve a period of over three or four days of eating low-fiber food, followed by two days of consuming nutritious liquids and colonoscopy prep solution.


In some cases, following the specialized food intake plan and using laxatives are sufficient to empty the bowel. However, other people, particularly those who are suffering from constipation, may need additional assistance to empty the bowel before their colonoscopy. If the bowel is not fully empty following colonoscopy prep, an enema will be prescribed.

The type of enema which is incorporated into colonoscopy prep is called a cleansing enema. It involves injecting liquid into the bowel via the rectum. This helps the body to push out any remaining waste. The liquid which will be used is usually a water-based solution with a small concentration of stool softener. The volume of water stimulates the movement of the large intestine, which in turn stimulates the bowels to expel both the solution and any remaining fecal matter.

If the bowel is not completely cleansed following an enema, the process can be repeated one or two more times. It is possible to undergo an enema in hospital, or to purchase an enema kit to carry out this process at home. The doctor will identify the most suitable option for the individual undergoing the colonoscopy.

Preparing for a colonoscopy: travel plans

A person can undergo a colonoscopy as an outpatient in most cases, arriving at the clinic and returning home the same day.

However, people undergoing a colonoscopy are usually given sedatives to help them relax and to ensure that they are comfortable during the colonoscopy. In all cases where sedatives are used, it is advisable to arrange for a friend or family member to accompany the person having the colonoscopy to and from the hospital. This is because, in general, avoiding activities such as driving is recommended for a time after the use of sedatives. The timeframe of this period depends on the specific sedative used.

Colonoscopy preparation FAQs

Q: Can I take routine medications whilst I am following my colonoscopy prep plan?
A: In the run up to a colonoscopy, a person should take their routine medication as normal. On the day of the procedure, if it is scheduled for the morning, avoid taking any medication unless specified by medical personnel, with the exception of blood pressure, heart and seizure medication. If a colonoscopy is scheduled for the afternoon, a person may take their routine medication, other than medications that they were instructed to avoid.

Good to know: Pain medication that is part of the NSAID group, like ibuprofen or aspirin, has historically not been recommended for use for several days or even more than a week before screenings where an additional procedure that causes bleeding is scheduled, such as a biopsy or polypectomy. This is due to the perceived increased risk of postoperative bleeding. 7

However, some recent research suggests that there may not be a need to avoid all NSAIDs. The increased risk of bleeding needs to be examined by differentiating between the different types of NSAID medicine, as not all of them will increase the risk in all cases. NSAIDs should only be used on a doctor’s recommendation. They will recommend NSAIDs based on criteria including: 8

  • Whether continuing or stopping medications that may already be in use will be better for the affected person
  • The overall risk of bleeding complications during the procedure
  • Whether the risk of bleeding complications will be increased by the particular painkiller used
  • The risk of encountering a problem due to stopping the use of the painkiller, if used continuously.

Always follow a doctor’s recommendations closely before taking any medications, including NSAIDs, before a colonoscopy.

Q: What can I do to reduce feelings of hunger during my colonoscopy prep?A: It is normal to feel hungry whilst preparing for a colonoscopy, particularly in the liquid-only stage. It is important to follow the food intake plan in order to ensure that the prep is effective. Drinking sodas with a high sugar content can help to keep feelings of hunger at a minimum during this stage. Feelings of hunger are expected during this stage of prep and should not be a cause for concern; if hunger is excessively bothersome or results in feelings of pain, please consult the doctor.

Q: What do I do if colonoscopy prep medication makes me vomit?
A: If the laxative solution makes you feel nauseous, the best thing to do is to take a break from your intended dose schedule and leave a longer interval before taking the next dose. Missing a dose should be avoided, and it is therefore important to drink a replacement dose if vomiting occurs after drinking the solution. Other tips that may help reduce the likelihood of nausea and the risk of vomiting, and which are alternatives to drinking the solution straight, include:

  • Drinking the prep solution in small sips
  • Sucking hard candy or a chilled lemon slice in between sips
  • Using a straw
  • Chilling the prep solution and/or drinking cold water alongside it
  • Discussing the use of a suitable anti-nausea medication with your healthcare provider, if nausea is expected

Q: Can a colonoscopy detect colon cancer?
A: Yes. A colonoscopy may be used as part of the screening process to detect colon cancer; a screening will be ordered for anybody at high risk of colon cancer or if it is suspected. When somebody is undergoing treatment for colon cancer, a colonoscopy may be scheduled periodically in order to monitor whether the treatment is effective. 9 Feeling unwell? If you are concerned about the health of you or a loved one, get a free symptom assessment with the Ada app.

Q: Are polyps removed during a colonoscopy?
A: During the colonoscopy procedure, it is possible to remove most polyps that are detected, in their entirety. This process is called polypectomy and can be performed using a range of different techniques, including removing the polyps with the help of an electrical current or cutting them off with a wire. In most cases, a person can undergo polypectomy during their colonoscopy as an outpatient. 10

Q: How long do you poop after colonoscopy prep solution is taken?
A: Most colonoscopy prep solutions begin working two to three hours after they are consumed, although this varies between products. Another dose may be needed if bowel movements do not occur when expected. If bowel movements do not occur after an additional dose, consult your medical care team. An extended prep time may be needed, and the scan may need to be rescheduled if it is not possible to cleanse the colon in time.

Q: What are the colonoscopy prep guidelines for people with diabetes?
A: A person who is affected by diabetes and is due to undergo a colonoscopy will need to agree to a personalized colonoscopy prep plan with their doctor. In some cases, a person’s food intake plan and their normal dosing plan for taking insulin and other medications may need to be altered to accommodate colonoscopy prep. Their medical care team will work closely with them to ensure that their treatment regimen for diabetes is not disrupted in a way which could be harmful. People with diabetes who also have reduced kidney function will be prescribed a specialized laxative, rather than using generic colonoscopy prep products. 11

Q: How long does diarrhea last after colonoscopy prep?
A: For some people, diarrhea continues for a short amount of time after the procedure. A small amount of leakage may occur in the hours after the scan, and people may therefore be recommended to wear protective clothing and/or use fluid absorbing pads in their underwear during this time. A person’s food choices in the immediate period after their colonoscopy are believed to influence the likelihood of experiencing diarrhea; it is recommended to avoid fried food, and to opt for a healthy, solid meal. 3

Q: Is there such a thing as a colonoscopy bag?
A: Colonoscopy and colostomy sound similar, but they are different procedures, and there is no such thing as a colonoscopy bag.

A colonoscopy is a scan of the colorectal area, and does not involve a bag. In contrast, a colostomy, or bowel diversion, is a surgical procedure used to divert one end or a loop of the large intestine out through the wall of the abdomen or belly. An incision is made in the skin and through the abdominal wall to create an opening called a stoma, sometimes also known as an ostomy. Over this, a small pouch – known as a colostomy bag – is placed in order to collect excreted stool and other human waste.