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What is a colonoscopy?

A colonoscopy is a procedure that lets your doctor see the inside of your entire colon—or large intestine. It uses a flexible tube with a light and a camera to look for signs of various colon conditions, and it’s also a commonly performed screening test for colorectal cancer.  

In some cases, your doctor may use a colonoscopy to take tissue samples or remove abnormal tissue. For example, polyps can be removed during colonoscopy to prevent them from progressing to colon cancer.

Watch Dr. Amaning address some common colonoscopy questions

Why might I need a colonoscopy?

You might need a colonoscopy for polyp and colon cancer screening, or to diagnose and determine treatment for a digestive condition. Early detection is key to preventing and reducing the risk of colon cancer and a colonoscopy can detect colon cancer even if you have no symptoms.

If you are having digestive symptoms, a colonoscopy may allow your doctor to diagnose the source of your symptoms, so you can choose the appropriate course of treatment.

  • Screening

    Together, colon cancer and rectal cancer are among the top five types of cancer diagnosed each year in the United States. But with routine screening for colorectal cancer using a colonoscopy, you can detect this common cancer type before you ever have symptoms or even prevent it from developing.

    For people with an average risk, guidelines from the U.S. Preventive Services Task Force recommend that you start colorectal cancer screenings at age 45. If you have a high risk for colorectal cancer or a family history of colorectal cancer, your doctor may recommend a colonoscopy screening sooner.

  • Diagnosis

    Many different conditions cause similar digestive symptoms. A colonoscopy is one of the best ways for your doctor to look for signs of any condition inside your colon. It provides a clear view of the entire colon, which together with any other tests, can provide an accurate diagnosis.

    During a diagnostic colonoscopy, your doctor may take tissue samples. These samples are sent to the lab for testing. Some of the digestive conditions diagnosed with a colonoscopy include:

  • Treatment

    Along with screening and diagnosis, a colonoscopy allows your care team to immediately treat some conditions during the procedure. For example, polyps or abnormal tissue can be removed during a colonoscopy and sent to a lab for imaging. If there is a blockage, a stent can be placed.

At what age should you get a colonoscopy?

You should talk to your doctor about colorectal cancer screenings, including colonoscopy, beginning at age 45. In 2021, the age to start colorectal cancer screenings was lowered from age 50 to 45, as colon cancer rates are rising in younger people.

Early screening for higher risk 

Talk to your care team if you have a family history of colorectal cancer, have inflammatory bowel disease, have a hereditary colorectal cancer syndrome or have any other risk factors. If your risk is high, the age at which you start screening may be earlier than those with an average risk. 

doctor in scrubs performing a colonoscopy on a patient

How often should you get a colonoscopy?

If your colonoscopy screening is normal, then you typically only need to repeat the screening every 10 years. Based on other findings like polyps, inflammatory bowel disease and family history, some people need to repeat a colonoscopy more frequently.

Once you reach age 75, you should talk with your doctor to decide if continuing screening is right for you based on your health needs.

How to prepare for a colonoscopy

To get ready for your colonoscopy, you’ll need to do a prep ahead of time to clean out your large intestine. This is important to give your doctor a clear view of the inside of your entire colon, so be sure to follow your doctor’s specific instructions.

It’s helpful to review your prep instructions several days before your procedure so that you can shop for supplies ahead of time. You’ll also want to talk to your doctor about any medications or supplements you take, as you may need to stop taking some of these before your procedure.  Make sure you plan to have a support person with you on the day of your colonoscopy to drive you home after your procedure.

The colonoscopy procedure

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A colonoscopy is a routine outpatient endoscopy test, meaning it doesn’t require you to stay in the hospital overnight. Your care team will give you anesthesia to put you to sleep or use sedative medications. While the procedure is quick, it requires preparation, including dietary changes, a few days before in addition to drinking the laxative solution.

Many people are hesitant to have a colonoscopy because of the prep, but your care team can provide helpful tips and instructions for your procedure. Today, there are various medication options available to help you prepare for your colonoscopy. Talk with your doctor about the right prep for your needs.

Before the procedure

Your doctor will give you step-by-step instructions on diet changes and adjustments to medications (if needed) in the days before your procedure. A few days before your colonoscopy, it is recommended to begin eating a diet low in fiber.  The day before your procedure, you’ll need to switch to a clear liquid diet—meaning you can only have liquids like water, broth, black tea or coffee, sports drinks, soda, or juice—avoiding anything with red, blue or purple dyes.

Depending on the time of your colonoscopy, you’ll take laxative medications—either in liquid or pill form—the evening before or in the evening and the morning of your procedure. These medications will make you go to the bathroom often to clean your colon. Plan to stay near a bathroom, make yourself comfortable and keep any needed supplies with you until your prep is complete.

During the procedure

When you arrive for your colonoscopy, you’ll change into a gown, get an intravenous (IV) drip and have the chance to ask your care team any questions. Once in the procedure room, you’ll lie on your side with your knees bent. You typically won't remember the colonoscopy procedure because you’ll have sedative medication or anesthesia.

Your doctor will start by guiding the scope, a thin, lighted tube with a camera, through your rectum, all the way to the top of the colon. You may have air pumped into your colon to make it easier to see. Then, the scope is slowly moved from the top of your colon to your rectum. As the scope is guided through your colon, your doctor can examine the tissue, look for signs of digestive conditions, take images or tissue samples, or remove polyps.

How long does colonoscopy take?

A colonoscopy usually takes 30 minutes. The procedure time can vary if tissue samples are taken or polyps are removed.

After the procedure

Most people only need a short time in the recovery area before they can go home after a colonoscopy. However, it may take 24 hours for anesthesia to wear off. You’ll need someone to drive you home, and you should avoid driving, working or making important decisions for the rest of the day.

Your first bowel movement may cause some bloating, gas or a small amount of blood. However, most people are back to normal activities the next day. Your care team will give you symptoms to watch for that signal a need to call your doctor.

Understanding the results

Your doctor will talk to you about the initial results of your colonoscopy right after you wake up from your procedure. If tissue samples were sent to the lab for more testing, those results typically take a few days. Based on the visual exam of your colon and any pathology results, you’ll be given either a normal or abnormal result for your procedure.

Normal results

A normal result means nothing abnormal was found. Your colon looked normal and healthy and showed no signs of cancer or a digestive condition. Most people will follow up with another colonoscopy screening in 10 years, but you may need one sooner if you have other risk factors like a family history of colon cancer.



Abnormal results

An abnormal result means your care team found an abnormality in the colon. This could include changes in the tissues due to a variety of digestive conditions, including inflammation, diverticulosis, narrowing, scarring or bleeding. You could also receive an abnormal result if your doctor finds precancerous or cancerous polyps. Depending on what is found, your doctor will work with you to confirm your diagnosis and plan your next steps.

Frequently asked questions

  • Are you awake during a colonoscopy?

    Most colonoscopy procedures are performed while you are asleep. You’ll go to sleep in the procedure room and then wake up in recovery. Different types of anesthesia and levels of sedation are available, so talk to your doctor about your choices.

  • Do colonoscopies hurt?

    No. Colonoscopies don’t usually hurt. You may feel bloated after the procedure.

  • What kind of doctor does a colonoscopy?

    Colonoscopy is performed by a gastroenterologist or colorectal surgeon. These doctors are specially trained in digestive health and endoscopic procedures—including colonoscopy.

  • Can I take Tylenol before a colonoscopy?

    Yes, Tylenol (acetaminophen) is OK to take before a colonoscopy if you need to take a pain reliever. In the days leading up to your procedure, you should avoid any non-steroid anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen (Advil or Motrin), naproxen (Aleve), and arthritis medications.

  • Can a colonoscopy detect IBS?

    No. A colonoscopy isn’t used to detect IBS—or irritable bowel syndrome. Unlike inflammatory bowel disease (IBD), IBS doesn’t cause changes in the tissue of the colon. If you have IBS, the lining of the colon would still appear normal during a colonoscopy.

  • What age should a woman get a colonoscopy?

    Women should follow the same guidelines as men and start routine colonoscopy screening at age 45 if they have an average colorectal cancer risk. Both women and men can significantly reduce the risk of colon and rectal cancer by following these screening guidelines.

  • Can you get a colonoscopy while pregnant?

    It is safe to get a colonoscopy during the second trimester of pregnancy, but it’s not a common choice. Doctors usually only recommend it if there is an immediate medical need.