Signs and Symptoms of Colon Cancer

Colon cancer is a type of cancer that occurs when harmful cells in the colon (large intestine) or rectum (the part of the large intestine that connects to the anus) begin to grow uncontrollably. The condition can cause painful symptoms such as changes in bowel habits, blood in the stool, stomach pain, fatigue, and lack of appetite, among others.

Keep in mind: these symptoms can mimic signs of other stomach or intestinal conditions, so experiencing these symptoms doesn't automatically mean you have colon cancer.

In many cases, colon cancer does not cause symptoms until it grows and spreads. Screening tests, such as a colonoscopy, can help detect colon cancer in its early stages when it is easier to treat. If you think you may have symptoms of colon cancer, it's a good idea to make an appointment with your healthcare provider to get tested. Receiving an early diagnosis can help you get started on treatment sooner which can improve your symptoms and life expectancy.

Local Symptoms 

Most colon cancers develop from polyps—or, growths of tissue that can develop in the colon or rectum. Polyps are usually benign (non-cancerous) and can usually be safely removed by a healthcare provider. If left untreated, some polyps can grow and divide abnormally, which can cause a cancerous tumor to form.

Early-stage colon cancers don't typically cause noticeable symptoms. If symptoms do occur, they tend to affect the area where the cancer originates or is located, which is known as "local symptoms." Local symptoms of colon cancer occur in the colon and rectum, which can cause symptoms such as changes in your bowel movements and stool, stomach pain, and bloating.

Changes in Bowel Habits 

Although most people experience a change in bowel habits from time to time, colon cancer can cause persistent changes that may last more than a few days. If you notice changes to your bowel habits, you might be experiencing:

  • Ongoing diarrhea or constipation
  • An urgency to use the bathroom
  • Pain or strain during bowel movements
  • The need to pass stool after you've just gone (known as incomplete bowel movement)

Blood in the Stool 

Rectal bleeding or blood in the stool can be an early warning sign of colon cancer. You might notice:

  • Stool that has streaks of bright red blood or a darker, tar-like appearance
  • Remnants of blood in the toilet bowl
  • Blood on toilet paper after you wipe

Bloody stools or bleeding from the rectum can be alarming but aren't always a sign of colon cancer. Hemorrhoids and anal fissures, for example, can also cause bleeding during a bowel movement. However, bloody stools are serious and if you notice blood in your bowel movement, you should always see a healthcare provider to understand the cause of this symptom.

Changes in Stool Shape 

A tumor in your colon can sometimes cause a blockage in your rectum. As a result, the appearance or general shape of your stool might look different than what you're typically used to. When this occurs, your stool can look abnormally thin or stringy. Think: similar to the appearance or size of ribbon.

The texture, color, and overall consistency of the stool may also change. Sometimes these changes can occur even without the presence of blood in your stool.

Abdominal Pain  

If cancer cells begin to grow and create the formation of a tumor, you might experience abdominal (stomach) pain or cramping. This can occur because a tumor in your colon can put pressure on your digestive system.

A tumor can also cause inflammation in your colon, leading to stomach pain and discomfort. Generally, you might experience a dull or achy sensation in your stomach that you may notice after eating. In some cases, gas and bloating can also accompany the pain.

Systemic Symptoms 

Unlike local symptoms, systemic symptoms occur when cancer cells have spread to other parts of the body. If your cancer spreads, you might experience changes in your weight, energy levels, and appetite.

Unintentional Weight Loss 

People with colon cancer can sometimes lose weight without meaning to or trying. Unintentional weight loss might occur for several different reasons:

  • The tumor interferes with your body’s ability to digest food and absorb nutrients properly, causing the body to break down stored fat and muscle tissue
  • Colon cancer causes your body to produce fewer digestive enzymes, making it difficult for you to absorb nutrients and thus resulting in weight loss
  • Cancer cells can cause inflammation and change the way your metabolism works
  • Symptoms such as diarrhea and loss of appetite may reduce how often you're eating

Fatigue and Weakness 

Colon cancer can make you feel exhausted, drained, and weak. As opposed to regular fatigue, cancer-related fatigue may cause you to feel bone-tired all the time, even after you had a relaxing day or a good night's sleep.

Excessive fatigue is more common in advanced stages of colon cancer, but can occur in earlier stages as well. You might experience this level of exhaustion due to a tumor using your body's energy to continue growing, intestinal bleeding which can cause anemia, or inflammation.

Loss of Appetite 

Loss of appetite is a common symptom of many types of cancer. Colon cancer may cause a loss of appetite when:

  • The tumor is blocking part of the colon, interfering with the digestion of food, or making you feel full even if you have not eaten
  • Your cancer cells or tumor releases hormones that affect how the body recognizes hunger and sends hunger signals to the brain
  • Nausea and diarrhea interfere with appetite, making you less likely to want to consume food

Advanced Stage Symptoms  

If colon cancer has advanced to later stages (e.g., stages 3 and 4) or metastasized (spread) to other parts of the body, you might have symptoms such as:

  • Swollen abdomen: Advanced colon cancer can cause swelling, pain, and discomfort in the abdomen. If the cancer has spread to the liver, you can also experience fluid build-up in your stomach.
  • Bone pain: If cancer cells spread to your bones, you can feel intense bone or joint pain and be at an increased risk for fractures.
  • Difficulty breathing: Sometimes, colon cancer spread to your lungs in an advanced stage. As a result, you might experience shortness of breath, coughing, chest pain, and wheezing.

When to See a Healthcare Provider 

If you have persistent symptoms of colon cancer or may be at risk of developing the condition, the best thing you can do for yourself is to schedule a visit with your healthcare provider. Many conditions can cause symptoms similar to colon cancer symptoms, and your provider can help determine the cause of your symptoms and provide an accurate diagnosis.

When you meet with your healthcare provider, they will typically ask you which symptoms you're experiencing, how long you have had symptoms, and how severe the symptoms have been. They may also perform a physical exam and order additional diagnostic tests that can help them look for any signs of cancer.

If you have a family history of colon cancer, talk to your healthcare provider about screening options. Early detection, diagnosis, and treatment can help boost your chances of successful treatment outcomes.

A Quick Review 

Colon cancer occurs when harmful cells grow out of control in the colon or rectum, causing a tumor to form and spread. Common symptoms of colon cancer include changes in bowel movements and stool, stomach pain, fatigue, and unintentional weight loss. In the early stage of colon cancer, you might not experience any noticeable symptoms—which can sometimes make the condition difficult to diagnose.

If you begin to experience any symptoms of colon cancer or notice a change in your digestive or bowel health, it's a good idea to see your healthcare provider for testing. Having a family history of the condition may also prompt you to visit your provider for screening options and early diagnosis. While receiving a diagnosis of colon cancer can be scary, knowing about your condition early can improve symptoms and expand your life expectancy.

Was this page helpful?
10 Sources uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. What is colorectal cancer?

  2. American Cancer Society. What is colorectal cancer?

  3. American Cancer Society. Do I have colorectal cancer? Signs, symptoms and work-up.

  4. Merck Manual: Consumer Version. Colorectal cancer.

  5. National Cancer Institute. Types of colorectal cancer.

  6. Centers for Disease Control and Prevention. What are the symptoms of colorectal cancer?

  7. Kuo YH, Shi CS, Huang CY, Huang YC, Chin CC. Prognostic significance of unintentional body weight loss in colon cancer patients. Mol Clin Oncol. 2018;8(4):533-538. doi:10.3892/mco.2018.1582

  8. Kasprzak A. The role of the tumor microenvironment cells in colorectal cancer (CRC) cachexia. Int J Mol Sci. 2021;22(4):1565. doi:10.3390/ijms22041565

  9. American Cancer Society. Loss of appetite. 

  10. Cancer Research UK. Advanced bowel cancer symptoms.

Related Articles