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About Your Colonoscopy

How to Prepare for Your Colonoscopy

This video will help you understand what a colonoscopy is and what to expect as you prepare for your colonoscopy.

Video Transcript

Colonoscopy is a procedure that examines the lining of the large intestine, also called the colon, and occasionally the very end of the small intestine, also called the terminal ileum. A screening colonoscopy is performed to look for small growths in the large intestines called polyps that may turn into cancer. Colonoscopy can also be performed to evaluate for blood in the bowel movement, changes in bowel habits, weight loss, low blood count, belly pain, family history of colon cancer or polyps, or abnormal stool tests.

Before starting the colonoscopy, the gastroenterologist or anesthesiologist will give you medications to help you relax and possibly fall asleep. After you are sleepy, a thin tube with a lightened camera at the end of the tube, called a colonoscope, is inserted into the large intestine.

The tube is carefully advanced to the beginning of your colon and sometimes into the small intestine. Polyps may be removed, and small tissue samples, called biopsies, may be taken during the procedure. During the procedure, you may experience gas and bloating as air and water help see the lining. It is essential to clean the colon well before the procedure so that polyps and other abnormalities are not covered up by stool.

Before preparing for your colonoscopy, please read and follow the written instructions from the doctor who ordered your exam. If you cannot locate your instructions, please contact the GI Nurse at the number noted here: 

  • GI Procedures lab: 312.996.3809
  • GI Nurse 312.413.0223 or 312.413.7676 

If you are receiving sedation during your colonoscopy, please make sure that you have a designated driver who is at least 18 years old and can accompany you back home after your procedure. You can only take public transportation, such as a cab, Uber, Lyft, or Meta car if an adult accompanies you after your colonoscopy. This is the policy of the hospital to ensure patient safety. Please do not bring any valuables or jewelry with you on the day of your procedure.

At the time that your colonoscopy is scheduled, please notify your primary doctor if you are taking any blood thinners or diabetes medications. These medications may need to be held or changed prior to the day of your procedure. If you are taking medications for high blood pressure, asthma, seizure, or heart disease, please continue to take these medications as usual with a sip of water at 6 am the morning of your colonoscopy.

Your doctor will provide you with a bowel preparation medication to help safely empty your colon of stool for your colonoscopy. Some of the most common medications include Golytely, NuLytely, Miralax, Moviprep, and Suprep. Please pick up your bowel preparation medication from the pharmacy approximately one week prior to your colonoscopy.

One week before the date of your colonoscopy, please review the instructions that were given to you on how to safely take your bowel preparation medication. If you are unable to locate your instructions, please contact the GI Department at the numbers listed below:

  • GI Procedures lab: 312.996.3809
  • GI Nurse 312.413.0223 or 312.413.7676 

Most preparation medications begin as a powder that must be mixed with the liquid to form a solution before, they can be taken. Please carefully follow your instructions on how to safely prepare your medication. After it is mixed, the bowel preparation solution can be stored in the refrigerator for a couple of hours prior to drinking. The prepared solution must be used within 48 hours.

For Morning Procedures

If your colonoscopy is scheduled in the morning before 12 pm, please drink one-half of your bowel preparation solution between 7 pm and 9 pm the night prior to your colonoscopy. Finish the remaining one-half of the solution on the morning of your colonoscopy between 4 am and 6 am. Do not eat or drink anything after 6 am.

For Afternoon Procedures

If your colonoscopy is scheduled in the afternoon, please drink half of your bowel preparation solution between 7 pm and 9 pm the night prior to your colonoscopy. Finish the remaining half of the solution on the morning of your colonoscopy between 5 am and 8 am. Do not eat or drink anything after 8 am.

It is common to experience mild nausea, bloating, stomach cramping, headaches, and dizziness while drinking your bowel preparation. Some patients may also experience vomiting. If you experience these side effects, try drinking the solution more slowly. If your symptoms are severe, stop drinking the solution and notify the GI doctor on call. Continue to drink water and liquids while you drink the bowel preparation solution.

Your first bowel movement should occur approximately one hour after starting to drink the bowel preparation. It is best to drink all the solutions to have the cleanest colon possible. Do not take other laxatives while taking your bowel preparation medication unless specifically mentioned by your doctor.

These mason jars filled with coffee show the importance of a clean colon. After you have finished drinking all your bowel preparation solutions, ideally, your stool should be clear and yellow, as noted in the picture on the right. 

If your stools are dark with solid material on the day of your procedure, your doctor may have difficulty seeing polyps, and the colonoscopy may be rescheduled. 

The following are tips to help you clean your colon for your colonoscopy.

One week prior to your colonoscopy, please avoid eating corn, nuts, seeds, popcorn, multi-grain breads, or raw vegetables, as they take longer to empty from the colon. The full day before your colonoscopy, do not eat any solid foods. Drink only clear liquids for breakfast, lunch, and dinner.

On the day before your colonoscopy. Examples of clear liquids include the following:

  • Water
  • Lemonade
  • Clear juices such as apple or white grape juice,
  • Coffee or tea without milk or creamer,
  • Clear carbonated drinks such as sprite or ginger ale
  • Sports drinks such as Gatorade, popsicles, or jello that do not contain pieces of fruit or seeds.

Please avoid eating or drinking red- or purple-colored drinks, popsicles, or jell as they can change the color of the lining of the colon.

Many patients do not enjoy the taste of bowel preparation solutions. Drinking the bowel preparation solution chilled with a straw can make the solution more palatable. Sucking on mints or other hard candy can also make the solution more palatable. Make sure you wear loose-fitting clothing, as the prep can make you feel bloated or gassy. Stay close to the toilet, have plenty of toilet paper, use skin-soothing wipes such as baby wipes, and keep yourself entertained as you prep with a book, laptop, or tv.

And finally, it is very important to drink all the bowel preparation solutions to have the cleanest colon possible. If you have any questions regarding your preparation instructions, please contact the GI Department at the numbers listed below:

  • GI Procedures lab: 312.996.3809
  • GI Nurse 312.413.0223 or 312.413.7676  

We look forward to seeing you soon!




We provide colonoscopies for colorectal cancer screening for new and established patients in our state-of-the-art GI & Endoscopy Lab.

If you are a patient interested in scheduling a screening or follow-up colonoscopy, please call 312.413.7676 and leave a confidential voicemail message with your name, date of birth, and telephone number. We will contact you within five business days to schedule your appointment.

If you are a healthcare provider outside the UI Health system who wants to refer a patient for screening colonoscopy, please download the referral form (docx) and fax to our scheduling department at 312.413.3798. Our staff will contact your patient and schedule a screening colonoscopy appointment.

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