Colorectal cancer screening

Screening for cancer of the colon and rectum starts at age 45, and there are several good test options.

Rosa: Hi, I'm Rosa. Colon cancer screening saves lives, and there is more than one way to do it. Let's find the test that works for you.

Colorectal cancer is cancer of the colon or rectum, which are parts of the large intestine. Most of these cancers start as small growths called polyps. Screening can find polyps and remove them before they turn into cancer.

The U.S. Preventive Services Task Force (2021) and the American Cancer Society both say adults at average risk should start screening at age 45 and continue through age 75. For ages 76 to 85, it is a personal choice based on your health and past screening. Most people over 85 should stop.

There is more than one good test. The best test is the one you will actually do. Some tests are done at home with a stool sample. Others are done at a clinic or hospital. Talk with your doctor about the pros and cons of each.

If a home stool test or a computed tomography (CT) colonography is not normal, you will need a colonoscopy. This is an important next step. Do not skip it. A positive stool test does not mean you have cancer, but the follow-up colonoscopy is how doctors find out.

Some people need to start earlier or be tested more often. This includes people with a parent, brother, sister, or child who had colorectal cancer or advanced polyps, people with inflammatory bowel disease, and people with certain inherited conditions like Lynch syndrome.

Blood tests for colorectal cancer are now available. The American Cancer Society says they are not a first choice, because they are less likely to find polyps. They may be an option only if you will not do any of the other tests. Do not wait for screening if you have bleeding from the rectum, blood in your stool, or changes in your bowel habits that do not go away.

Colonoscopy

A doctor uses a thin tube with a camera to look inside the whole colon and remove polyps. You get medicine to help you relax or sleep. If it is normal, it is usually repeated every 10 years.

FIT (fecal immunochemical test)

A home test that checks a small stool sample for hidden blood. It is done every year.

Stool DNA test

A home test that checks stool for blood and for changes in cells shed from the colon. It is usually done every 3 years.

CT colonography

Also called a virtual colonoscopy. A computed tomography (CT) scan makes pictures of the colon. You still need a bowel prep. It is done every 5 years.

Flexible sigmoidoscopy

A shorter tube looks at the lower part of the colon. It is done every 5 years, or every 10 years with a yearly FIT.

Bowel prep

Drinking a special liquid the day before a test to clean out the colon. A good prep helps the doctor see clearly.

Polyp

A small growth on the inside wall of the colon. Some polyps can turn into cancer over time.

• If you are 45 or older, ask your doctor which test is right for you.
• Tell your doctor if family members had colon cancer or polyps, and at what age.
• If a home test is positive, schedule the follow-up colonoscopy right away.
• Ask if you will need a ride home after a colonoscopy. Most places require one.
• Write down when your next test is due.

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.