Excluding skin cancers, colorectal cancer is the third most common type of cancer in Americans and the third leading cause of death from cancer in the U.S., according to the American Cancer Society.

Screenings can catch it early when it’s treatable.

The growing number of people getting preventive screenings has brought the colorectal cancer death rates down, showing that screening really does work.

The Centers for Disease Control and Prevention and the U.S. Preventive Services Task Force recommend that everyone 45 to 75 years old get a screening. Most health plans cover this type of preventive screening with no out-of-pocket costs when you go to your primary care provider or medical group (for HMOs) or a doctor or medical center in your plan’s network (non-HMO plans).*

If you have a family history of colon cancer or have other conditions that could lead to colon cancer, your doctor may want you to start getting tested earlier than age 45. Keep in mind that a family history or other conditions may mean that your test is not considered a preventive screening. It could be considered a diagnostic test. That means you may have out-of-pocket costs for your test.

Talk to your doctor about when to start colon cancer screening and how often to get tested.

How Does Colon Cancer Start?

Colon cancer usually begins with a growth called a polyp that develops in the inner lining of the colon. These polyps grow slowly over a period of many years. When polyps first start to develop, they are not cancer yet, but they have the potential to become cancer. The risk that a polyp will become cancerous increases as it gets larger.

Polyps can be removed easily before they have a chance to become cancer. Once a polyp does become cancer, it gets more difficult to treat.

Precancerous polyps and early colon cancer may not show symptoms. A screening test is the best way to prevent colon cancer or catch it early for a better chance at successful treatment.

What Are the Symptoms?

Since early colon cancer may not have any symptoms, screening is critical. By the time you develop symptoms, it may have grown and spread, making it harder to treat.

But there are some warning signs you can watch for, including:

• Anemia, which causes symptoms such as weakness, excessive fatigue and sometimes shortness of breath
• Bleeding from the rectum
• Blood in the stool or in the toilet after having a bowel movement
• Dark or black stools
• A change in bowel habits or the shape of the stool that isn’t caused by a change in diet
• An urge to have a bowel movement when the bowel is empty

While some people may develop these symptoms, they often only become noticeable as the cancer gets worse and becomes harder to treat. Screening before symptoms are present is the only way to diagnose the cancer early enough to more successfully treat it and prevent complications.

What Are the Screening Options?

Colonoscopy is the most common preventive screening tool.  It is also the most effective screening test for colon cancer.

A doctor uses a colonoscope — a flexible, lighted tube with an attached camera — to look at the entire rectum and colon for signs of cancer. The doctor can even remove precancerous polyps during the procedure, preventing you from getting cancer.

Some people may avoid a colonoscopy because it sounds painful. But since you're asleep during the procedure, it doesn't cause most people discomfort, and it takes less than an hour.

Other screening options are available, but they are not as effective as colonoscopy. You can ask your doctor about these options:

• Fecal immunohistochemical test (often called FIT or FIT kit): A fecal occult blood test: A lab scans a stool sample for blood, a possible sign of cancer.
• Sigmoidoscopy: This procedure is similar to a colonoscopy, but it looks only at the rectum and the lower colon.
• Virtual colonoscopy: A CT scan supplies detailed images of the colon.

If one of these tests detects a problem, your doctor will likely recommend a diagnostic colonoscopy. Learn about the difference between preventive screening colonoscopies and diagnostic colonoscopies.

Early detection by screening is key. Catching it early gives you a better chance at successful treatment. Talk to your doctor about what screening options are best for you.

Can You Prevent Colorectal Cancer?

These healthy lifestyle tips may help to protect you from colon cancer:

• Eat a diet that’s high in fruits, vegetables and fiber.
• Stay away from red, grilled and processed meat.
• Avoid smoking, heavy use of alcohol and sedentary lifestyles.
• Exercise.
• Keep your weight in check.

*If you have a grandfathered plan (a plan that was in existence on or before March 23, 2010), preventive care without out-of-pocket costs may not apply to you.

Sources: Colorectal Cancer: Screening,  U.S. Preventive Services Task Force, 2021; Colorectal Cancer Facts & Figures 2020-2022,  American Cancer Society, 2020; Colorectal Cancer Statistics,  Centers for Disease Control and Prevention (CDC), 2024; Reducing Risk for Colorectal Cancer,  CDC, 2024; Screening for Colorectal Cancer,  CDC, 2024

Originally published 2/12/2020; Revised 2020, 2022, 2023