Irritable bowel syndrome (IBS) and colon cancer symptoms look alike. However, unlike IBS, colon cancer may cause bloody stool, fatigue, and unexplained weight loss, among other unique symptoms.

IBS is a chronic disorder of your large intestine. Your bowel or large intestine is the end of your digestive tract, known as the colon.

Because IBS and colon cancer each affect the same part of your body, the symptoms look the same. So, it’s best to know the difference between the two.

Although some symptoms of IBS and colon cancer are the same, there are some differences to keep in mind.

This chart summarizes how IBS and colon cancer can appear similar and how they may differ. Read on to learn more details about each.

SymptomIBSColon cancer
abdominal cramps or pain related to bowel movementsXX
changes in bowel habits lasting more than a few daysXX
feeling that bowel movements are incompleteXX
bloating or excess gasXX
whitish mucus in stoolX
dark stool or blood in stoolX
general weaknessX
narrowing of stoolX
rectal bleedingX
unexplained weight lossX

Some of the most common symptoms of IBS are changes to bowel movements, including:

Other symptoms can include:

Certain foods, stress, anxiety, or depression can trigger symptoms of IBS. Even though it’s a chronic condition, these symptoms can come and go.

People assigned female at birth may experience increased symptoms during their period. This happens because of changing hormone levels.

For most people with IBS, symptoms aren’t serious and can be managed with lifestyle changes. Yet, those with severe symptoms may require medication to treat the condition.

To diagnose IBS, a doctor will want to know your medical history, including the following:

  • all the medications you take
  • recent infections
  • recent stressful events
  • basic diet and foods that seem to affect symptoms

Your personal and family history is also essential. This includes a history of:

A doctor will do a physical exam to check for abdominal bloating and tenderness. You may not need additional testing to get a diagnosis of IBS. Even so, some tests can rule out other conditions. These include:

A pattern of symptoms may help your doctor diagnose your condition. For example, you may have abdominal pain plus two or more of the following symptoms:

  • abdominal pain that gets better or worse after a bowel movement
  • movements that are more or less frequent than you’re used to
  • a change in the appearance of your stools

You may be told you have IBS if your symptoms began at least 3 months ago and you’ve experienced them over at least 3 days a month.

Symptoms of colon cancer can include changes to your colon and bowel habits that last for more than a few days, such as:

  • abdominal cramping or pain
  • constipation
  • dark stool or blood in your stool
  • diarrhea
  • excess gas
  • fatigue
  • a feeling that bowel movements aren’t complete
  • narrowing of the stool
  • rectal bleeding
  • unexplained weight loss
  • weakness

It’s recommended to consult a doctor as soon as possible if you develop a combination of these symptoms.

As with IBS, a doctor will want your complete personal and family medical history.

Risk factors may include:

Your doctor may order blood and stool tests and a physical exam. If cancer is suspected, other tests may include:

  • colonoscopy, along with tissue biopsy
  • imaging tests, such as X-ray or CT scan of your colon and rectum

Since colon cancer is slow-growing, colonoscopy screenings can catch precancerous polyps. Doctors can remove these polyps before they develop into cancer.

A polyp biopsy can confirm the presence of colon cancer, and imaging tests can help check if cancer has spread.

You may not feel like you need a colonoscopy, but colorectal cancer can be silent until cancer starts to spread. This is why routine screenings are so important.

IBS, with all its discomforts and inconveniences, rarely causes damage to your digestive tract or leads to other health problems.

In 2021, the American College of Gastroenterology (ACG) published clinical guidelines for managing IBS.

The ACG says that when undergoing colonoscopy, people with IBS were no more likely to have precancerous polyps or colon cancer than healthy people. Overall, most people with IBS have a healthy colonoscopy report.

Talk with a doctor if you have any concerns about abdominal discomfort or changes in bowel habits. Symptoms such as IBS can also point to other conditions, including colon cancer.

Red-flag symptoms that you should see a doctor right away include a combination of the following:

  • persistent abdominal pain
  • rectal bleeding
  • vomiting
  • weight loss
  • diarrhea during sleeping hours
  • iron deficiency anemia
  • family history of colon cancer, IBD, or celiac disease

Having IBS doesn’t increase your risk of colon cancer, but that doesn’t mean you should ignore symptoms. To be safe, tell your doctor about new symptoms such as rectal bleeding, narrowed stool, or weight loss.

Talk with a doctor about colon cancer screening. For most people, colonoscopy screening should begin at age 45.

If you have a family history of colon cancer or other risk factors, your doctor may recommend earlier or more frequent screening.

My doctor says anxiety is the cause of my IBS. Is this true?

Research shows that there’s a genetic link between stress, anxiety, depression, and IBS symptoms. That said, anxiety isn’t the main cause of IBS. Instead, a mix of diet, hormones, medical conditions, recent infections, and your ability to manage stress can contribute to IBS.

Does colon cancer cause mucus in stool?

A small amount of mucus in your stool is typical. Both IBS and colon cancer can cause this.

Still, mucus is much more common in people with IBS and may appear white. In colon cancer, mucus may appear bloody or dark black, along with other red-flag symptoms. Studies show mucus testing may be an important tool in the future to solve colon problems without a colonoscopy.

Are colon spasms a sign of cancer?

Colon spasms can happen in both IBS and colon cancer. They’re most common in IBS. Colon spasms can be a sign of cancer when the spasms occur along with other red-flag symptoms.

IBS can generally be managed by making specific dietary and other lifestyle changes. More severe cases can be treated with medications.

Having IBS doesn’t increase your risk of developing colon cancer.

Symptoms of colon cancer tend to appear only after the disease has spread. Screening for colon cancer can detect and remove precancerous polyps before they can become cancer.

Because the symptoms of IBS, colon cancer, and other gastrointestinal disorders overlap, it’s best to see a doctor to get the right diagnosis. They can help you manage or treat your condition so you can start feeling better.