You should begin passing clear or yellowish fluid at the end of the bowel prep process. If this liquid is free from fecal matter, it’s an indication that your bowel prep is complete.
This article discusses bowel prep before a colonoscopy, and how you can tell when the process is complete.
When Is Bowel Prep Complete?
The effects of bowel prep medication can begin as soon as 30 minutes to an hour after your first dose, and can last up to 16 hours. Most people do not continue to experience diarrhea after they’ve gone to bed on the night before the test.
When your bowel movements contain only brown liquids, this means you are almost finished with your bowel prep. Your stools should eventually end up as a clear or yellowish liquid. If there is any cloudiness to your liquid stool, your bowel prep is not complete.
Your stools may look clear before you complete your entire prep. It’s important to finish the prep anyway. You could still have stool higher in your colon that will come out later. Completing all steps of your prep offers you the best chance of having a clear colon for your colonoscopy (and not having to repeat the test).
If you can see the bottom of the toilet after a bowel movement, this means your bowel prep has been effective and the procedure can go forward.
Tips for a Successful Bowel Prep
There are a few things you can do before your bowel prep begins to ensure that it is complete in time for your procedure. Most importantly, make sure you follow all the instructions your healthcare provider gave you, and finish all of the prep as instructed, even if you think your bowels are clear.
In the few days prior to your bowel prep, stick to the diet recommended by your gastroenterologist. Eat smaller portions and drink plenty of fluids. Good food choices include:
SoupsSmoothiesDigestive tea like chamomile or peppermintLighter-colored foodsPasta and riceSteamed vegetablesEggsChicken
Avoid eating:
Nuts and seeds, including bread and other products that contain themPopcornHard-to-digest foods like cornRaw vegetablesRed meatFried foodsAnything containing purple, orange, or red dye
Your healthcare provider will advise you to consume a liquid diet during the day before your colonoscopy. Choose liquids that are pleasant to drink, such as:
White grape juiceChicken broth7-Up or Sprite
Try chilling your bowel prep first and drinking it through a straw. This can help prevent nausea and vomiting. If you vomit the medication, it may result in an incomplete prep.
Stay hydrated during the bowel prep. Drink only clear fluids. In particular, make sure to avoid anything containing purple, orange, or red dye. These dyes can look like blood and may interfere with the results of your colonoscopy.
What to Do if You’re Still Passing Stool
If the morning of the test arrives and you’re still passing stool, or if you’re passing a cloudy, brown liquid, you may need to take additional steps to finish clearing your colon. Your healthcare provider will give you specific instructions on how to do this. Some steps that may be recommended include:
Drinking a bottle of liquid magnesium citrate (up to 4 hours before the procedure) Drinking large amounts of clear fluids (up to 2 hours before the procedure) Using an over-the-counter enema
If these strategies don’t work, contact your healthcare provider. You may need to reschedule the exam, since your healthcare provider won’t be able to adequately visualize your colon if there is still stool present.
Why Bowel Prep Matters
According to research published in the journal Gastroenterology, up to 25% of colonoscopies are canceled due to an unsuccessful bowel prep.
Deciding to cancel your procedure is not an easy decision for a healthcare provider to make if you are already sedated and the practitioner has already started the procedure. The healthcare provider can only continue with your colonoscopy if your colon is completely clean.
Sometimes you may have the exam but receive inadequate results if there is still stool in your colon. This often happens when people skip one of the steps of the prep because they believe they are done. It can also happen because they don’t think all of the steps are necessary.
Summary
Before you get a colonoscopy, it’s important that you follow the bowel prep directions given to you so that you know when the prep is done. Your stools should be clear, yellowish liquid near the end of the prep.
But don’t stop then: Make sure to complete all the steps in the directions. Closely following these instructions will help ensure the colonoscopy is effective.
A Word From Verywell
Preparing for a colonoscopy isn’t exactly fun, but it’s an important exam that can help you live a long, healthy life. By following your healthcare provider’s bowel prep directions, you will prepare for the colonoscopy effectively so you can get reliable answers from this test.
Depending on your doctor’s instructions, you may need to wake in the middle of the night to take a second dose of laxatives. Known as a split-dose bowel prep, the second dose should be taken at least four to six hours before the scheduled procedure.
An enema typically begins working in about five minutes but may take up to an hour to work back out. If you have a long drive to the testing center, you can take the enema two hours before your need to leave for the appointment.
