What At-Home Colon Cancer Tests Are Available, and How Reliable Are They?

Experts recommend colon cancer screening for most adults starting at age 45. The goal of screening is to find early cancers or precancerous polyps (growths in the colon) that can become cancerous over time. Screening for colon cancer can be life-saving. When colon cancer is found early and before it spreads, about 9 in 10 people diagnosed will be alive after 5 years.

When most people think of colon or rectal cancer screening, they think of a colonoscopy (a camera test that looks at the inside of the large intestine, or colon). While a colonoscopy is the most accurate screening tool, it’s not the only test out there. In fact, you can perform your own colorectal screening test in the comfort of your own home. 

We’re here to help you understand how accurate and reliable these at-home tests are and when it’s best to visit a provider instead.

How do at-home colon cancer tests work?

The FDA has approved three types of at-home tests for colon cancer. They work by testing a sample of your stool (feces or poop). This makes them convenient to do at home. The tests work by looking for blood or DNA in the stool that could be from colon cancer. 

Most cancers bleed into the colon or rectum. You may not be able to see the blood, but colon cancer tests can detect it.

Here are the different types of at-home tests.

Guaiac fecal occult blood test 

Guaiac fecal occult blood test (gFOBT) uses a chemical called guaiac to look for occult blood in the stool (blood that isn’t visible to the naked eye). 

To do the test, you collect stool samples from three separate bowel movements. You use a stick or swab to take a small sample of stool and apply it to a test card. Your kit will come with instructions and the materials you need to collect your samples. 

You need to stop certain medications (like NSAIDs), vitamin C supplements, and some foods a few days before doing the test. This is because certain foods and medications can cause false-positive or false-negative results. This means the test comes back as positive or negative when the real result is the opposite.

Fecal immunochemical test 

Like gFOBT, the fecal immunochemical test (FIT) detects blood in the stool. The difference is that it uses antibodies (instead of guaiac). 

FIT is used more often than gFOBT because it’s easier to do. You only need to collect one sample, and you don’t need to stop any foods or medications before the test. FIT is also more likely to give accurate results than gFOBT. 

Stool DNA test

This test checks the stool for DNA from cancerous or precancerous cells in the colon. Cancer cells (and normal cells) from the colon can be detected in the stool. The stool DNA test also checks for blood (hemoglobin). 

To do the test, you’ll need to collect a whole stool sample for the test (compared to the small sample needed for gFOBT and FIT). You don’t have to change your diet or stop any medications before doing the test.

How do you get the results?

After you collect the sample, follow the specific instructions and send it back to a lab for testing. The kit will have information about how you’ll get the results. 

If your healthcare provider ordered the test, they’ll get the results and then share them with you. If an at-home colon cancer test is positive, the next step should be a colonoscopy. Your provider can help you understand your results and discuss next steps with you.

Common problems with colon cancer home screening

A colon cancer screening test is only useful if a lab can process the sample that you send. To make sure your sample gets processed, follow the instructions carefully when collecting and sending a stool sample. 

A large study found that more than 1 in 10 samples of FIT tests could not be processed by a lab. The most common reasons for this were:

• Not enough stool sample

• Incorrectly labeled sample

• Old samples

• Broken or leaking containers

This study looked specifically at FIT tests, but similar problems can happen for all kinds of at-home stool tests. Make sure to label the samples as directed and follow instructions for how much stool to include. And don’t wait long to send it to the lab. If your sample can’t be processed, send another sample. 

Who should use at-home colon cancer tests?

At-home screening tests are best for people with an average risk of colon cancer. This means you don’t have risk factors for colon cancer other than age. 

You have a higher risk for colorectal cancer if you have any of the following: 

• A history of colon cancer or polyps

• A family history of colon cancer or polyps

• Inflammatory bowel disease (like Crohn’s disease and ulcerative colitis)

• A personal or family history of a high-risk disease (like Lynch syndrome or familial adenomatous polyposis)

If you have any of these risk factors, at-home screening tests may not be right for you. Other screening tests, like a colonoscopy, may be better. Your healthcare provider can help you decide on the best way and time to screen for colon cancer for your unique situation.

How often should you check for colon cancer with an at-home test?

How often you screen for colon cancer depends on which at-home test you use. If you have an average risk for colon cancer, here’s the recommended timing by test: 

• gFOBT: every year

• FIT: every year

• Stool DNA testing: every 3 years

What are the pros and cons of at-home colon cancer tests?

Like with most things, there are pros and cons to at-home colon cancer tests.

Pros

If you have average risk for colon cancer, at-home tests have many pros that may make them a good option for you: 

• Convenience: You can do at-home tests at any time. Test kits for each type of home stool-based test will give you the supplies and instructions you need. 

• No appointments: Compared to a colonoscopy, you don’t need to take time off from work or arrange transportation. 

• No bowel prep or sedation: There’s no need for bowel prep (emptying your bowel ahead of time), and the tests don’t require anesthesia or sedation like a colonoscopy.

Cons

At-home colon cancer screening needs to happen more frequently. With the gFOBT or FIT, yearly screening is recommended. With a stool DNA test, you should screen every 3 years. In comparison, a colonoscopy should be done every 10 years (if the results are normal and you don’t have other risk factors). 

Beyond frequency, some people may not be comfortable handling stool samples. And you run the risk of finding out that you didn’t provide an adequate sample for testing, in which case you’ll need to provide another sample. 

Can you buy colon cancer tests over the counter?

You can buy some colon cancer screening tests over the counter at your local pharmacy or online. You’ll need a prescription from your healthcare provider for stool-based DNA tests. But you can buy some gFOBT and FIT tests without a prescription. 

To make sure you get the best test, your healthcare provider can often give you a test kit at your appointment or help you find a test that’s right for you.

How accurate and reliable are at-home colon cancer tests?

While colonoscopy is the best test for colon cancer screening, at-home colon cancer tests are also accurate. FIT is better at accurately detecting colon cancer compared to gFOBT. For this reason, FIT is often preferred over gFOBT. That said, both FIT and gFOBT have been shown to decrease deaths from colon cancer. 

Stool DNA tests can give positive results that aren’t really positive. The downside of this is it can lead to more colonoscopies being done for tests that aren’t actually abnormal.

Are at-home colon cancer tests a good alternative to a colonoscopy?

Colonoscopy has a 100% detection rate for colon cancer. A provider performs a colonoscopy using a long, thin instrument with a camera on the end. This lets them see inside the colon and remove any polyps.

So how do at-home screening tests compare? For people at average risk of colon cancer, at-home stool tests can be a good alternative to colonoscopy. And doing an at-home test is much better than not screening for colon cancer at all. For people with a higher risk of colon cancer, a colonoscopy is the best screening test. 

When to see a doctor for colon cancer screening

At-home colon cancer tests are only used for screening. They’re not for diagnosing colon cancer. If you have symptoms that could be from colon cancer, talk with your healthcare provider before doing any testing. 

Colon cancer symptoms can include: 

• Weight loss

• Abdominal pain

• Blood in the stool

• A change in bowel habits 

Although these symptoms can be from colon cancer, there are also other causes. Your healthcare provider can make sure you get the right testing to figure out the correct diagnosis.

Why trust our experts?

Written by:

Sarah Pozniak, MD

Sarah Pozniak, MD, has 9 years of experience since graduating medical school (6 since completing residency). She is a board-certified general internal medicine physician and has practiced as a primary care physician in both Utah and Washington, D.C. Currently, she cares for patients with chronic illnesses such as diabetes and high blood pressure using telemedicine as part of a virtual care program.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

Reviewed by:

Karen Hovav, MD, FAAP

Karen Hovav, MD, FAAP, has more than 15 years of experience as an attending pediatrician in a variety of clinical settings. She has worked in a large academic center in an urban city, a small community hospital, a private practice, and an urgent care clinic.

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