A colonoscopy typically takes 30 to 60 minutes, and most of that time you’ll be sedated enough that you won’t remember much of it. The procedure involves a flexible tube with a camera being guided through your colon while a doctor looks for polyps, inflammation, or other abnormalities. Here’s what actually happens at each stage so you know what to expect.
Before the Scope Goes In
You’ll change into a hospital gown and lie on your left side with your knees drawn toward your chest. This left-side position is standard because it aligns with the natural curve of your colon and makes insertion easier. A nurse will place a small clip on your finger to monitor your oxygen levels and attach a blood pressure cuff. Your heart rate, blood pressure, and oxygen saturation are tracked continuously throughout the procedure.
An IV line goes into your arm for sedation. At this point, the medical team will confirm your identity, review your medical history, and check that your bowel prep worked well enough to give the doctor a clear view.
How Sedation Works
Most colonoscopies use one of two sedation approaches. Conscious sedation, the more common option, uses a combination of a sedative and a pain reliever through your IV. You stay technically arousable, meaning someone could wake you, but many people drift off entirely and remember nothing afterward. The experience varies from person to person: some feel relaxed and drowsy, others sleep through the whole thing.
Deep sedation uses a faster-acting medication administered by an anesthesiologist or nurse anesthetist. With this approach, you’re fully asleep. Recovery from deep sedation tends to be quick, though you may feel groggier immediately afterward. Your doctor’s office will typically tell you in advance which type of sedation they use, and you can ask about your options.
What Happens During the Procedure
Once sedation takes effect, the doctor inserts a colonoscope, a thin, flexible tube about the width of a finger, through the rectum. The scope has a tiny camera and light at the tip, along with channels that allow the doctor to pump in gas to gently inflate your colon. This inflation is necessary because the walls of the colon naturally sit collapsed against each other, and spreading them apart gives the camera a clear view.
The doctor navigates the scope through the entire length of your colon, roughly five feet, section by section. The scope bends and turns to follow the natural curves, and the doctor uses air or water to keep the view clear. Many facilities now use carbon dioxide instead of regular air for inflation because it’s absorbed by the body much faster. In studies comparing the two, patients who had carbon dioxide reported significantly less bloating afterward.
The goal during insertion is to reach the very end of the colon, where it connects to the small intestine. Once there, the doctor slowly withdraws the scope, and this withdrawal phase is actually where the most careful inspection happens. The doctor examines every fold and surface of the colon lining on the way out, looking for polyps, abnormal tissue, or signs of disease.
What It Feels Like
If you’re under deep sedation, you won’t feel anything. With conscious sedation, you may feel mild pressure, cramping, or a sensation of bloating as gas inflates your colon. Some people feel brief moments of discomfort when the scope navigates tighter turns, particularly in the lower left portion of the colon where there’s a natural S-shaped curve. If you’re awake enough to notice discomfort, the medical team can adjust your sedation in real time. You may be asked to take slow, deep breaths to relax your abdominal muscles.
Most people who receive conscious sedation report little to no memory of the procedure afterward, even if they were technically awake during parts of it. The sedative medications used commonly cause short-term amnesia, which is considered a feature, not a side effect.
If Polyps Are Found
Polyps are small growths on the colon lining, and removing them during the colonoscopy is one of the main reasons the procedure prevents colorectal cancer. If the doctor spots a polyp, they remove it right then, no second procedure needed. You won’t feel this happening.
The removal technique depends on the polyp’s size. Small polyps are typically grabbed with tiny forceps passed through a channel in the scope. A gentle pull detaches the polyp cleanly from the colon wall. For medium-sized polyps, the doctor uses a wire loop called a snare that lassoes the polyp at its base and cuts through it, sometimes with a mild electrical current that simultaneously seals the tissue to prevent bleeding. Larger polyps (about two centimeters or bigger) require a more involved technique where fluid is injected beneath the polyp to lift it away from the colon wall before snaring, which reduces the risk of damaging deeper tissue.
All removed tissue is sent to a lab for analysis. Your doctor will typically have pathology results within a week or two, and those results determine when you’ll need your next colonoscopy.
Complication Risks
Colonoscopy is one of the most commonly performed procedures in gastroenterology, and serious complications are rare. The two main risks are perforation (a small tear in the colon wall) and bleeding.
Perforation occurs in roughly 1 in 2,000 screening colonoscopies. A large French study of nearly one million colonoscopies found a perforation rate of 0.04%. Bleeding is more common but still infrequent. For screening colonoscopies without polyp removal, the bleeding rate is well under 1%. When polyps are removed, the risk increases modestly to about 1% or less, depending on the size and number of polyps taken. Most post-polypectomy bleeding is minor and stops on its own.
Recovery and Getting Home
After the scope is removed, you’ll be wheeled to a recovery area where nurses monitor your vital signs as sedation wears off. Average recovery time is under 50 minutes. Before you can leave, the staff checks that you’re alert, breathing normally, and stable enough to walk. Some facilities use a formal scoring system that evaluates your oxygen levels, blood pressure, breathing, consciousness, and ability to move. You need to hit a certain threshold on two consecutive checks before discharge.
The most common sensation in recovery is bloating and gas from the air used to inflate your colon. This passes, literally, within an hour or so. You may also feel mildly groggy or lightheaded from sedation. Because the sedative affects your coordination and judgment for the rest of the day, you’re required to have someone drive you home. Most facilities won’t discharge you unless your ride is present.
Your doctor or a nurse will usually give you a brief summary of findings before you leave, including whether any polyps were removed and when the pathology results will be available. Because sedation can impair memory formation, it’s worth having your companion listen in or asking for written instructions. Many people find they can’t recall this conversation the next day.
You can eat and drink normally after the procedure. Most people feel completely back to normal by the following morning, though mild bloating or cramping can linger for up to 24 hours. If polyps were removed, you may be advised to avoid heavy lifting or blood-thinning medications for a few days.