Bowel Prep: What You Need To Know

What Is Bowel Prep?

Woman touching stomach, mid section, close-up
Philip Nealey/Digital Vision/Getty Images

What Is Bowel Prep?

Bowel preparation, commonly known as "bowel prep", is the process of removing all feces from the colon in order to have a medical or surgical procedure such as a colonoscopy.

It is important to clean the colon of all stool, food particles and anything else that may be present for several reasons. If you are having surgery on or near the colon, having stool present is a risk for infection and can get in the way of some procedures.

A full colon can make it difficult to operate upon adjacent tissues, such as the uterus. Think of the colon as a balloon taking up room in an already tight space. An empty colon, like a deflated balloon, takes up far less room and gives a surgeon far more room to work.

There are times when a bowel prep is done purely to prevent potential complications from surgery. For example, if your bowel was nicked during surgery, the infection risk would be dramatically decreased if the bowel was empty.

In the case of a colonoscopy, stool in the colon can prevent the surgeon from seeing the tissue that is being inspected and would make it very difficult to introduce the lighted scope into the rectum and colon. Imagine a plumber trying to clean a clogged pipe in your home and compare that to a pipe that is completely clean and clear, and you will understand why your doctor wants your colon as clean as possible.

For your own safety, and to have the best possible outcome from your procedure, it is imperative that you follow your bowel prep instructions to the letter.

How To Do an Effective Bowel Prep

How to Do Bowel Prep

Bowel prep procedures vary between doctors and between procedures. The bowel prep for someone who is having a colon surgery might be very different from someone who is having a colonoscopy.

Follow your doctor's instructions carefully, and err on the side of caution when you are in doubt. The goal is to have your digestive tract clear of all fecal material, food and anything else that may be present. If you are unable to do this, or if you do not follow the instructions, your procedure may be delayed or canceled.

Your bowel prep may consist of one step or several, depending on your physician's wishes. Most patients are required to drink a large amount of medicated fluid such as Go-Lytely, which will stimulate their digestive tract and cause copious diarrhea-like bowel movements. Some patients may have a large number of pills to take, rather than the solution. Other patients rely upon enemas to complete the bowel prep.

In rare cases, pills, fluid, ​and enemas will all be used, but one or two of these is typical.

Your doctor may also prescribe an anti-nausea medication such as Reglan, which also increases the speed at which your prep works.

If you normally take medications in the morning, do not take them without first consulting your physician. You may be asked to skip your medications for the day, or to take them after your procedure is complete.

Before and During Bowel Prep

What Not to Do Before and During Bowel Prep

You may be given detailed instructions for your bowel prep prior to your procedure. These typically include the time when you must stop eating, and when you should begin your bowel prep.

Resist the temptation to have a heavy meal as your last meal. Many people eat a large last meal as though they will never have the opportunity to eat again.  Remember, you will basically be cleansing your digestive tract of everything you have eaten in the last few days, so adding a large amount of food immediately before your bowel cleanse will just make it take longer.

Do not eat solid foods. Your doctor may allow you to have clear liquids during your bowel prep and after, but that only includes foods that are liquid and clear at room temperature. You may not have Jello or other soft foods unless specifically instructed by your doctor.

Do not stop your bowel prep without informing your doctor. An incomplete or inadequate bowel prep, typically caused by not following the instructions carefully and completely, can increase the length of your procedure.

In some cases, if you fail to complete your bowel prep properly and your procedure is canceled, you may be liable for the cost.

Helpful Hints and Tips For Bowel Prep

  • If you are on a low-sodium diet, or must avoid sodium, be sure to mention this to your physician. Some bowel prep solutions contain significant amounts of salt.
  • If you are diabetic, be sure that your physician is aware of this. Going for extended periods of time without food may cause issues, so be sure to have a plan in place for low blood sugar.
  • Even though you may be drinking a large volume of bowel prep solution, you still need to take in fluids as you normally would. Water is ideal, but clear liquids (preferably not carbonated) are acceptable.
  • Avoid high-residue foods and fiber supplements in the days before your procedure. Corn and nuts are examples of a high-residue food, which often is visibly unchanged when it is expelled from the body.  A low residue diet is beneficial in the day or two prior to a bowel cleanse. 
  • Keep your bowel prep solution cold, if possible; this can reduce how much you taste it. You may also want to drink it through a straw.
  • You may experience urgency, and need to get to the bathroom very quickly. If you are not able to move quickly or need assistance to get to the restroom, plan to stay close to the bathroom. If you decide to sleep during bowel prep, be aware that you may have difficulty waking and moving to the bathroom quickly enough to avoid accidents.
  • Consider purchasing high-quality (very soft) toilet paper for your bowel prep. You will be going to the bathroom frequently, and soreness may develop if you use a harsh paper.
  • Consider purchasing wet wipes for your bowel prep to use instead of toilet paper. They are gentler and may prevent irritation when wiping frequently is necessary. 
  • Get comfortable and wear clothes that can easily be removed, such as pajama pants or a nightgown. You will be spending a lot of time going to the bathroom, and you may just get to the point where you just stay on the toilet instead of getting up and going every few minutes.
  • Dress warmly. You will be spending a great deal of time in the bathroom on a cold toilet seat, partially undressed. Do your best to make sure you aren't cold along with everything else that is going on. Some people wrap themselves in a blanket.
  • If you are given a solution that you must drink, consider flavoring it to make it more palatable. Crystal Light and Kool Aid are common choices. You may not want to use something that you enjoy on a regular basis, such as your favorite lemonade mix, as it may no longer be appealing after bowel prep.
  • If you are feeling lightheaded during your bowel prep, slow your intake of the bowel prep solution. Also, try to push/bear down less, as this can cause a feeling of lightheadedness.
  • It is possible for the bowel prep process to remove some of the normal flora of your intestines. This can make it more difficult to digest food, or just make your system feel "off" in the days following your procedure. Adding yogurt with active cultures to your diet as soon as soft foods are permitted can help with this issue.

Bowel Prep Risks and Side Effects

Risks of Bowel Prep

In general, bowel prep is very safe, and most patients have no true medical problems with the procedure. The vast majority of bowel prep patients do, however, have a great deal of discomfort during the process.

Many patients say that the bowel prep is worse than the actual procedure the prep is done for, as you are asleep or sedated for a colonoscopy or surgery.

Common Side Effects of Bowel Prep

(May be present in up to half of all patients doing bowel prep)

  • Cramping
  • Nausea
  • Feeling of Fullness
  • Fecal Incontinence
  • Changes in Taste
  • Vomiting
  • Sweating

Rare Side Effects of Bowel Prep

  • Seizure
  • Shortness of Breath
  • Facial Redness
  • Chest Pain
  • Heart Palpitations
  • Muscle Weakness
  • Acute Renal Failure

Any of these signs/symptoms should be reported to your doctor immediately.

Dehydration During Bowel Prep

Dehydration is common when doing a bowel prep if you are not taking in adequate fluids during the process. While you may be required to drink up to 8 ounces of bowel prep solution every ten minutes, if you aren't taking in water in addition to the solution, you could become dehydrated.

Signs of dehydration include:

  • Dizziness
  • Decreased Urination
  • Headache
  • Stomach Cramps
  • Rapid Heart Beat


Bowel preparation at home: Prospective study of adverse effects in elderly people. Heymann, Chopra, Nunn, Coulter, Westaby and Murray-Lyon. British Medical Journal.

GI Bowel Prep Implicated In Causing Renal Failure. Smiley Thakur.

Medication Guide HalfLytely and Bisacodyl Tablet Bowel Prep Kit. Food and Drug Administration.

Continue Reading