IBS vs. Colon Cancer: How to Tell the Difference

Health Line

21-05-2025

Irritable bowel syndrome (IBS) and colon cancer symptoms can 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 can look the same. If you have IBS, it can be helpful to understand what signs may indicate something more serious and when you should speak with a doctor.
IBS vs. colon cancer symptoms
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.
Symptom IBS Colon cancer
abdominal cramps or pain related to bowel movements X X
changes in bowel habits lasting more than a few days X X
constipation X X
diarrhea X X
feeling that bowel movements are incomplete X X
bloating or excess gas X X
whitish mucus in stool X
dark stool or blood in stool X
fatigue X
general weakness X
narrowing of stool X
rectal bleeding X
unexplained weight loss X
What are the symptoms of IBS?
Some of the most common symptoms of IBS are changes to bowel movements, including:
constipation
diarrhea
Other symptoms can include:
abdominal pain
bloating
excess gas
a feeling that bowel movements are incomplete
whitish mucus in your stool
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 can be managed with lifestyle measures. However, those with severe symptoms may require medication to treat the condition.
Diagnosing IBS
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:
celiac disease
colon cancer
inflammatory bowel disease (IBD)
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:
Blood tests to check for infections, anemia, and other digestive problems.
Stool tests to check for infections, the presence of blood, and other diseases.
A pattern of symptoms may help a 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 three months ago and you've experienced them over at least three days a month.
What are the signs and symptoms of colon cancer?
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 speak with a doctor as soon as possible if you develop a combination of these symptoms.
Diagnosing colon cancer
As with IBS, a doctor will ask for your complete personal and family medical history.
Risk factors may include:
colorectal polyps
Crohn's disease
familial adenomatous polyposis
family history of colorectal cancer
hereditary nonpolyposis colon cancer, also known as Lynch syndrome
lack of physical activity
unhealthy diet
type 2 diabetes
ulcerative colitis
A 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 (tissue growth). 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.
When to see a doctor
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 a 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.
Can IBS lead to colon cancer?
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.
Frequently asked questions
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.
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.
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.
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.
Takeaway
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 connect with a doctor to get the right diagnosis. They can help you manage or treat your condition so you can start feeling better.