Colonoscopy: What to Expect Before, During and After

Q: Can you have an EGD and a colonoscopy on the same day?

Yes. An EGD ( upper endoscopy ) looks at the food pipe, stomach and first part of the small intestine through the mouth. Doctors often do both under one sedation, for example to look for the cause of a low iron level. The EGD is usually done first.

A colonoscopy is an exam of the inside of your large intestine (colon and rectum) using a long, thin, flexible tube with a camera on the end. It’s the main test to screen for colon cancer, because the doctor can find and remove growths called polyps during the same exam. You are given medicine to make you sleepy, so most people feel little or nothing.

Key points

Most adults at average risk should start colon cancer screening at age 45. A normal colonoscopy usually doesn’t need repeating for 10 years.
A clean colon matters. You’ll drink a strong laxative (the bowel prep) the evening before and often again that morning.
The exam itself takes about 20 to 45 minutes. You’ll need someone to drive you home.
Serious problems are uncommon. Bleeding after polyp removal is the most frequent one.
Call your doctor for heavy bleeding, severe belly pain or fever in the days after the test.

Why a colonoscopy is done

Cancer screening. Colon cancer often starts as a polyp, a small growth on the lining. Removing polyps stops many cancers before they form. People with a family history, past polyps, or Crohn’s disease or ulcerative colitis may need to start earlier and repeat it more often.
Follow-up of another test. A positive stool test (such as FIT or a stool DNA test), a blood screening test, or an abnormal CT scan needs a colonoscopy to find out why.
Symptoms. Doctors use it to look for the cause of blood in the stool, long-lasting diarrhea, a change in bowel habits, belly pain or a low blood count from iron loss.

Stool tests and CT colonography (a “virtual colonoscopy”) are other ways to screen. They can’t remove polyps, so any finding still leads to a colonoscopy.

Getting ready for a colonoscopy

Your clinic will give you written steps. Follow them closely, because a poorly cleaned colon can hide polyps and you may need to repeat the test.

A few days before: Many clinics ask you to eat low-fiber foods and skip seeds, nuts, popcorn and raw vegetables. Stop iron pills if told to.
The day before: Switch to clear liquids, such as water, broth, apple juice, plain gelatin, and tea or coffee without milk. Avoid anything red or purple.
The prep: You’ll drink a laxative solution, usually split into two doses. The second dose is often taken 4 to 6 hours before the test.
Medicines: Tell your doctor in advance if you take blood thinners, insulin or other diabetes medicines, or weekly weight-loss shots such as semaglutide or tirzepatide. Some need changes before the test. Don’t stop any medicine unless told to.
A ride: Arrange for an adult to take you home.

What to expect after drinking the prep

The prep works by drawing large amounts of water into the bowel, which flushes stool out. Frequent, urgent, watery bowel movements usually start within 1 to 3 hours. Bloating, cramps, nausea and feeling chilled are common. Stay near a bathroom, drink plenty of the allowed clear liquids, and use soft wipes or a barrier cream to protect your skin. When it is working, what comes out should look like clear or yellow liquid.

The bowel prep is different from “colon cleanse” products and colon hydrotherapy sold for detox. Those aren’t needed for health and can cause harm.

During the colonoscopy

You’ll change into a gown, and a nurse will place a small tube (IV) in your arm. You lie on your left side with your knees bent. Medicine through the IV makes you very drowsy or puts you into a light sleep.

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The doctor, usually a gastroenterologist, gently passes the scope through the anus and up through the whole colon. Air or carbon dioxide opens the bowel so the doctor can see. You may feel pressure or cramping if you’re awake. The doctor can take tiny tissue samples (biopsies) and remove polyps with a wire loop. You can’t feel this.

The procedure is the same for women and men. Women who have had a hysterectomy or other pelvic surgery may find the scope a little harder to pass. You can ask for a female doctor or a chaperone, and you should tell the team if you could be pregnant.

After a colonoscopy

You’ll rest for 30 to 60 minutes while the sedation wears off.
Bloating and gas pains are normal. Walking and passing gas help.
Don’t drive, work, drink alcohol or sign important papers until the next day.
A little blood with your first bowel movement can happen after a biopsy or polyp removal.
Your first normal bowel movement may take a day or two.

Possible risks

A colonoscopy is a common and generally low-risk test, but problems can happen:

Bleeding. This happens in about 1 in 100 people who have a polyp removed. It can start right away or up to 2 weeks later. Most bleeding stops by itself or is treated with another scope.
A tear in the bowel wall (perforation). This is rare, fewer than 1 in 1,000 exams. It usually needs surgery.
Reactions to sedation, such as breathing or heart rhythm problems.
Dehydration or salt imbalance from the prep, mostly in older adults or people with kidney disease.
Missed polyps. No test is perfect, and the risk is higher when the colon isn’t clean.

Your results

The doctor usually tells you what they saw before you go home. Biopsy and polyp results take about 1 to 2 weeks. Your doctor will then say when you need your next colonoscopy. This may be 10 years if all is normal, or sooner if polyps were found.

When to call your doctor

Call right away, or go to an emergency department, if you have:

More than a few spoonfuls of blood, or blood clots, in your stool
Severe or worsening belly pain, or a hard, swollen belly
Fever of 100.4°F (38°C) or higher, or chills
Vomiting, dizziness or fainting

Common questions about colonoscopy

Is a colonoscopy painful?

Most people feel little or no pain because sedation makes them drowsy or asleep. Some have mild cramping or pressure during the exam and gas pains afterward. For many, the bowel prep is the hardest part, and it is uncomfortable more than painful.

What should I eat after a colonoscopy?

Most people can go back to their normal diet the same day. Start with a light meal, such as soup, eggs, toast or rice, and drink plenty of fluids to replace what the prep took out. If polyps were removed, your doctor may suggest soft foods and no alcohol for a day or two.

Is bleeding after a colonoscopy normal?

A few drops of blood in the first bowel movement or two can be normal, especially after a biopsy. Bleeding can also start days later, up to about 2 weeks after a polyp was removed. Call your doctor for more than a small amount, clots, or bleeding with dizziness.

Can you have an EGD and a colonoscopy on the same day?

Yes. An EGD (upper endoscopy) looks at the food pipe, stomach and first part of the small intestine through the mouth. Doctors often do both under one sedation, for example to look for the cause of a low iron level. The EGD is usually done first.

When can I restart blood thinners after a colonoscopy?

Ask your doctor before you leave, because the answer depends on the medicine and on whether polyps were removed. Many people restart the next day. Don’t restart early or wait longer without advice, since both bleeding and blood clots are risks.