How to Prepare for a Colonoscopy (and Why It’s So Important)

Content medically reviewed by Dr. Kimberly Kolkhorst

If you're like most people, the idea of getting a colonoscopy doesn't sound like much fun. But it's an important part of taking care of yourself, and you might be surprised to find out that the process isn't as unpleasant as you might fear. By knowing how to prepare for a colonoscopy, you can help the procedure go smoothly while protecting your health.

"Colorectal cancer is the fourth most common type of cancer for both men and women, with the exception of skin cancer, and detecting it early can save lives," said Dr. Kimberly Kolkhorst, gastroenterologist at Essentia Health. "While you might have heard negative things about the process of getting a colonoscopy, the reality is that for most people, the procedure is easier than they realize and brings peace of mind. Many patients tell me, after the procedure, that it was much easier than they were expecting and they are glad they had it done!"

Why Colonoscopies Are the Gold Standard

Different tools are available for colorectal cancer screening. But most providers consider a colonoscopy to be the best option because it’s the only one that not only detects abnormalities but also helps with preventing colon cancer by removing precancerous polyps at the time of the procedure.

Almost all colorectal cancers begin as precancerous polyps, which are abnormal growths that can become cancer. During a colonoscopy, a gastroenterologist uses a thin, flexible tube with an attached camera to examine your rectum and colon, which make up most of your large intestine. If the provider sees any polyps, they can remove them, stopping potential cancer cells before they have a chance to grow. At Essentia Health, new technology allows for the detection of precancerous lesions in real-time.

Additionally, colonoscopies are the most accurate tool for detection, identifying approximately 95% of all colorectal cancers.

"Other colorectal cancer screening options include testing your stool for signs of cancer. These tests are not as accurate as a colonoscopy and have a risk of false positives," Dr. Kolkhorst said. "Certainly any screening is better than none, but I recommend everyone who is due for screening get a colonoscopy. It takes one day to get this done and that that one day can truly save your life!"

The American Cancer Society recommends beginning regular colonoscopies at age 45 for those at average risk. If your results are normal, you don’t need to repeat the procedure for 10 years. If you are at higher risk for colorectal cancer, your provider might recommend starting sooner, and you may need to be screened more often.

How to Prepare for a Colonoscopy

In order for your provider to get a clear view of your colon, you must clean out your bowel so your large intestine is clear of all or most stool. To do this, you must follow a special diet and do bowel prep before the procedure.

About three days before your colonoscopy, eat a low-fiber diet. This can include animal proteins, such as eggs, poultry, fish, and cheese; cooked vegetables, including carrots, pumpkin, green beans, and potatoes; low-fiber fruits, such as bananas, pears, and peaches; and low-fiber breads like white and sourdough.The day before your procedure, you will be on a clear-liquid diet. This means you cannot eat any solid food and you must drink plenty of clear liquids. Things you can eat or drink on this day include:

• Clear, fat-free broth or bouillon
• Clear juice, such as white grape or apple
• Clear sports drinks or sodas
• Lemon, lime, banana, or orange popsicles or gelatin (no cherry, grape, or raspberry, as the colors can stain your colon lining and make it difficult for your provider to examine it)
• Plain coffee or tea (no cream or milk added)
• Water

Late in the day, you will need to take laxatives to clean out your bowel. This might require taking pills or drinking a bowel prep solution. You will have diarrhea, so you will want to stay home, near a bathroom, during this part of your prep. When your bowel movements are clear yellow (not cloudy), you’ll know the prep is complete.

“Bowel prep is probably the least desired part of the colonoscopy experience for many people,” Dr. Kolkhorst said. “Some ways to make it easier include staying hydrated, drinking lots of broth, refrigerating the prep solution, and drinking the solution through a straw. Using wet-wipes can also help prevent peri-anal irritation from wiping.”

What Happens on the Day of the Procedure

On the day of your colonoscopy, you will likely not be able to eat or drink anything before the procedure. Your provider will give you specific instructions for taking medications. You may need to stop taking certain medicines, such as blood thinners, several days before the procedure.At the hospital or clinic, this is what you can expect:

• You will put on a hospital gown and a nurse will record your vital signs, including your blood pressure, pulse, and temperature, as well as the oxygen saturation level of your blood. Your heartbeat may be monitored with electrocardiogram patches.
• You will then lie on your side on an examination table, with the lower half of your body covered by a sheet. Your provider might ask you to raise one or both knees to your chest.
• Next, you will be given a strong sedative. You may still be conscious, but the medications will make you very relaxed, help to decrease the sensation of pain, and can cause transient amnesia, so you might not remember it. 
• The provider will insert a colonoscope into your rectum and thread it all the way to the end of your colon.
• As necessary, your provider will pump air into the colonoscope to widen the large intestine and get a better view.
• If needed, your provider will take a biopsy or stool sample from inside the colon.

After the colonoscopy is complete, your provider will talk to you or a family member about the procedure and whether they removed any polyps or took a biopsy.Because of the effects of the sedative, you will need to have someone drive you home. You can return to your normal diet right away.