A colonoscopy allows the doctor to look inside the colon. The colon is the lower portion of the GI tract and is about 5 feet long. Your doctor will use a small flexible tube to do a visual inspection of the inside of your colon. Your doctor may also do a biopsy and remove any polyps (small growths) found inside your colon during the procedure. A biopsy means that a small amount of tissue is taken from the lining of your colon. This tissue is studied closely to help determine your diagnosis and the best treatment for you.

Video: What to Expect From Your Colonoscopy Procedure

Preparing for the Test

Your colon will need to be cleaned thoroughly to complete the test. If this is not done correctly, the test will need to be rescheduled.

The medicines you receive during the colonoscopy will make you sleepy. Ask someone you know and are comfortable with to accompany you to drive you home after the procedure. If you do not have someone with you to drive you home, the procedure will be cancelled. It is a good idea to have someone with you through the remainder of the day and night. You will not be able to work, drive, or make any decisions for the rest of the day. You will not be allowed to use public transportation unless you are accompanied.

If you use oxygen at home, please bring a portable oxygen unit with you. This includes oxygen use when you sleep and/or are active. You may need to use the oxygen for a while after the procedure.

Avoid Metamucil and any foods with skins (tomatoes, apples), seeds, corn or nuts for a few days before your test.

Plan Ahead

  • Inform your doctor of all the medicines you take. You may be given specific instructions about certain medicines.
    • Notify your doctor if you take any blood thinners such as Coumadin, Plavix, Lovenox, Pradaxa, Xarelto etc.
    • Stop any Iron containing medicines or supplements 7 days before the colonoscopy.
    • Inform your doctor if you take any oral medicines or insulin for diabetes.
  • Purchase a supply of clear liquids for the day before the test. Clear liquids include Gatorade, fruit juices (no citrus), soda, popsicles without fruit or cream, gelatin without fruit, broth (skim the fat off the top), coffee or tea. Do not drink anything that is red or purple.
  • If you have a history of constipation, use Miralax, per package instructions, twice daily for 5 days before starting the prep the day before your procedure. Two days before the procedure, begin a diet of liquids only. Dairy products are allowed on this day. The next day you will begin clear liquids only.
  • Fill your prescription for HalfLytely at a pharmacy. This is a “kit” which will include one Bisacodyl tablet and a 2 liter plastic jug with powder in it. You will need to purchase one bottle of Magnesium Citrate.
  • If your insurance does not allow HalfLytely, Nulytely will be dispensed in a 4 liter jug. You will only use half of this and discard the remainder. You will also need to purchase the Bisacodyl. The pharmacist should be able to help you if you have questions. You will take one 5 mg. tablet.

The Day Before the Test

  • Do not eat any solid food the day before or the day of the colonoscopy.

  • Drink as much liquid as you can, the more liquid you drink, the better your prep will be. Remember, clear liquids only on the day before the procedure. Avoid drinking only water; you will get all your calories from the liquids you drink.

  • Mix the Halflytely as directed in the morning, place in the refrigerator to chill.

  • At 12 noon, take the Bisacodyl tablet with a large glass of water.

  • Between 4 and 6 p.m.; begin drinking the mixed Halflytely. Drink an 8-10 oz. glass every 15 minutes until the 2 liter bottle is consumed. If you have the 4 liter bottle, divide it into half. You will drink 2 liters or ½ of the jug. It should take between 2 - 3 hours to drink the solution. If you begin to feel bloated or nauseated, wait a little longer between glasses, walk around your house or yard, or rock in a rocking chair. If you vomit, wait for 20 to 30 minutes, and then resume drinking.

The Day of the Test

  • Do not eat or drink anything except as directed.
  • Drink the bottle of Magnesium Citrate 4 hours before your procedure.
  • Take only the medicines the doctor has asked you to take. These are generally heart or blood pressure medicines, or seizure medicines. They should be taken after you have finished the solution.
  • Bring your inhaled medicine with you.
  • If you have sleep apnea, bring your CPAP mask and machine with you.
  • If you are diabetic, please bring your glucose meter, test strips, and fast acting glucose source (either glucose tablets or gel).
  • Bring extra clothing, just in case you need it.
  • Check in at the check in desk in the front lobby at the time you have been asked to.


During the Test

When you arrive, the nurse will explain the procedure before, during, and after the colonoscopy. If you have any questions, please ask. The nurse will start an IV. The IV will be used to administer the sedation used during the procedure. You will be monitored closely during the procedure. You will be asked to lie on your left side. You may feel some pressure and cramping, but most people have no memory of the actual procedure. Once the procedure is completed, you will be taken to a room to recover. You will feel a little sleepy. Your doctor will determine when you are able to go home.

Length of Test

Plan on being at the doctor for at least 3 hours. The procedure only takes about 20 minutes, but you will need to recover before you can go home. Remember, you will need someone to drive you home. You will need to plan on resting the rest of the day.


This information has been approved by Philip D. Hanna, MD (February, 2013).

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