What are the signs and symptoms of colon cancer?

Dr. Jeanne Morrison, PhD
Family Practitioner

Colon cancer symptoms often center around the colon and digestive system. Rectal bleeding or bloody bowels for a few weeks are common. A person may also feel gassy or have painful cramps, and may feel like they cannot empty their bowel completely. They may also feel tired or weak and lose weight. In the early stages, colon cancer may present no symptoms.

Dr. Jill K. Onesti, MD
Surgical Oncologist

Colorectal cancer can cause symptoms of obstruction, as the tumor grows to a point where it blocks your colon or your rectum. You may notice this as pain in that area of your belly, difficulty in passing stool, or sudden onset of nausea and vomiting. If there is a partial blockage of the colon, your stools may appear narrower or thin in caliber—even as thin as a pencil. Another common symptom is seeing blood in your stools. It is important not to assume any blood in your stools is from a hemorrhoid, but rather discuss this with your doctor and undergo further evaluation.

Both benign colon polyps and malignant colon polyps may cause few or no symptoms. When colon cancer does cause symptoms, these symptoms may take the form of diarrhea, constipation, or narrowing of the stool as the tumor begins to interfere with bowel function. Typically, these symptoms would last for more than a few days. A tumor in the colon may also cause people to feel like they have to go, and the sensation is not relieved by a movement. Bleeding or blood in the stool and abdominal pain or cramping may also be signs of colon cancer.

However, all of the previously mentioned symptoms can also be the result of far less dangerous health problems, such as hemorrhoids or irritable bowel syndrome, so having these symptoms does not mean that a person has colon cancer. In fact, these symptoms are more likely to be due to a condition other than colon cancer.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

If caught early, colon cancer is one of the most curable cancers, which is why it’s important to know the warning signs. While polyps detected during colonoscopies are a risk factor, bloating can be a symptom. Bloating related to colon cancer is caused when the tumor blocks the colon, preventing gases and feces from moving through.

Other symptoms related to colon cancer include bloody stools, a change in the shape of your stool and the feeling you urgently have to urinate.

Starting at age 50, you need to have a colonoscopy every 10 years. If you have a parent or sibling with a history of colon cancer, start getting your colonoscopy 10 years before they were diagnosed.

Dr. Lisa Ganjhu, DO

The tricky thing about colon cancer is that doesn’t have a lot of obvious early-warning symptoms. Check out this video with gastroenterologist Dr. Lisa Ganjhu to learn the small and subtle cues you can clue into.

Dr. David Greenwald, MD

Colorectal cancer is often present in people without symptoms, making prevention and screening for colorectal cancer very important. A polyp may be found and removed even before it becomes cancerous or presents with symptoms; once symptoms appear, a colonoscopy is performed to aid in diagnosis, rather than screen for disease. 

The following signs or symptoms, however, might indicate colorectal cancer: 

  • blood in stools
  • narrower than normal stools
  • unexplained abdominal pain
  • unexplained change in bowel habits
  • unexplained anemia
  • unexplained weight loss

These symptoms may be caused by other benign diseases such as hemorrhoids, inflammation in the colon or irritable bowel syndrome. The presence of these symptoms for more than a few days is an indication to talk with a gastrointestinal specialist about these symptoms and the patient’s family history.

Dr. Steven V. Gurland, MD

The first sign of colon cancer is traces of blood found in the stool. As the cancer grows symptoms of changing bowel habits occur usually constipation. abdominal pain is associated with signs of obstruction. If not treated early it will spread and then numerous systemic symptoms can occur.

Very often, a lot of patients have trouble believing they have colorectal cancer because they do NOT have any symptoms. For others, they might have abdominal pain, bloating, change in bowel habit or weight loss. Unfortunately with symptoms, their cancer might already be advance. Another non-specific symptom might be bleeding. Since there we don't know if someone is constipated or have a colon cancer, it is advisable to see your doctor for any changes or concerns and to schedule a colonoscopy by age 50.

Often there are no symptoms of colorectal cancer, which is why screening is started at a certain age. Symptoms can include bleeding, anemia, abdominal pain and unexplained weight loss. Through screening it's possible to lower the cancer rates and, most importantly, lower the colorectal death rate.

Dr. Lawrence S. Friedman, MD

Colorectal cancer is the third most common form of cancer in both men and women, with an estimated 143,000 new cases diagnosed in the United States each year. Early on, colon cancer causes no symptoms. Later, its symptoms can be similar to those of inflammatory bowel disease (IBS)—abdominal pain, cramping, bloating, gas pains, and a change in bowel patterns. In addition, blood in the stool or rectal bleeding is often present. Advanced cancer is likely to cause bloody bowel movements, severe constipation if the intestine is obstructed, and weight loss. Thus, it's vital to get checked without delay should these symptoms occur.

The good news is that most cases of colon cancer can be prevented through screening. Almost all precancerous growths (polyps) can be spotted and removed during a colonoscopy. Early-stage, localized colon cancers are curable by surgery in 90% of cases.

In its early stage, colorectal cancer usually produces no symptoms. Polyps may be small and produce few, if any, symptoms. Some important warning signs include:

  • Any notable change in bowel movement consistency or frequency
  • Dark or light blood in the stool or rectal bleeding
  • Abdominal discomfort or bloating
  • Unexplained fatigue, loss of appetite and/or weight loss
Dr. Deborah M. Axelrod, MD
Surgical Oncologist

Colon cancer is highly treatable when found early, so it's important to know the symptoms so you can get them checked right away. In this video, cancer specialist Deborah Axelrod, M.D., discusses the colon cancer symptoms you should never ignore.

Colon cancer can have many different warning signs; early cancer usually doesn't not have any signs or symptoms, but things that should make you more concerned and be evaluated by a physician include noticing blood or a dark color with your bowel movements, persistent changes in the character of your bowel movements (e.g., diarrhea or constipation), cramping, gas, bloating, a feeling like there's still stool in your intestines despite just completing a bowel movement, weakness, fatigue or weight loss.

Colorectal cancer (cancer of the colon or rectum, both of which make up the large bowel) is most curable when found before it causes symptoms. When symptoms do occur, they might include:

  • Changes in bowel habits
  • Rectal bleeding or blood in the stool (bright red or very dark)
  • Abdominal (stomach) cramps or frequent gas pains or bloating
  • Unexplained weight loss or fatigue

The symptoms of colorectal cancer are bleeding, constipation, and general changes in the bowel movement. Yet, in most cases, there are no symptoms for colorectal cancer, which is why for the average risk individual should have a regular colonoscopy starting at the age of 50.

Colorectal cancer is often a silent disease, meaning it develops with no symptoms at all until it is very advanced. When symptoms do occur, they may include the following:

  • Blood in or on the stool
  • Change in bowel habits
  • Narrower stools
  • Bloating/fullness
  • Vomiting
  • Diarrhea, constipation or feeling of incomplete evacuation
  • Unintentional weight loss
  • Rectal bleeding
  • Constant tiredness or new fatigue

The colon is the largest part of the large intestine, also known as the large bowel. The colon's function is to change liquid waste into solid waste and prepare it to be expelled from the body.

Symptoms of colon cancer include:

  • Bleeding from the rectum
  • Blood (bright red or very dark) in the stool or toilet after a bowel movement
  • A change, or narrowing of the stool
  • Cramping or pain in the abdomen
  • Feeling the need to have a bowel movement, but not having one
  • Excessive fatigue
  • Frequent gas, bloating or feeling of fullness
  • Weight loss for no known reason
  • Nausea and vomiting

Rectal cancer is cancerous tissue that grows along and invades the wall of the rectum. Rectal cancer and colon cancer are very similar and share many common features. The difference in location creates important differences in how each is treated. Rectal cancer, like colon cancer, may start as a polyp that becomes cancerous.

Symptoms of rectal cancer include:

  • Change in bowel habits including: diarrhea, constipation, feeling that the bowel has not completely emptied, stools that are narrow in shape
  • Bright red or dark blood in the stool
  • Abdominal discomfort
  • Change in appetite
  • Losing weight without dieting
  • Fatigue

For colon cancer, here are signs to look for:

  • a change in bowel habits, such as persistent diarrhea or constipation
  • a change in the consistency of the stool that persists longer than four weeks
  • rectal bleeding or blood in the stool
  • a feeling that the bowel is not completely emptying
  • feeling weak or fatigued
  • weight loss for no apparent reason
  • persistent cramping, gas or pain, or overall abdominal discomfort

It is so important to get screened for colon cancer beginning at age 50 (or younger, with certain risk factors) and be aware of colon cancer's signs. Even though colonoscopies are an effective way of detecting and preventing colon cancer and thus, saving lives, too many people don't get them.

This content originally appeared on

A common symptom of colorectal cancer is a change in bowel habits. Symptoms include:
  • Having diarrhea or constipation
  • Feeling that your bowel does not empty completely
  • Finding blood (either bright red or very dark) in your stool
  • Finding your stools are narrower than usual
  • Frequently having gas pains or cramps, or feeling full or bloated
  • Losing weight with no known reason
  • Feeling very tired all the time
  • Having nausea or vomiting
Most often, these symptoms are not due to cancer. Other health problems can cause the same symptoms. Anyone with these symptoms should see a doctor to be diagnosed and treated as early as possible.

Usually, early cancer does not cause pain. It is important not to wait to feel pain before seeing a doctor.

This answer is based on source information from the National Cancer Institute.
Symptoms of colon cancer develop late in disease, which is why we screen patients at regular intervals rather than waiting for symptoms. Weight loss, change in bowel habits, unexplained abdominal pain, anemia, rectal bleeding, occult blood in the stool, or bowel obstruction can be signs of colon cancer.

Continue Learning about Colon Cancer

What You Need to Know About Colon Cancer
What You Need to Know About Colon Cancer
Colon cancer is the third leading cause of cancer-related deaths in American men and women separately, and the second most common cause of cancer deat...
Read More
What is hereditary nonpolyposis colon cancer (HNPCC)?
Honor Society of Nursing (STTI)Honor Society of Nursing (STTI)
Hereditary nonpolyposis colorectal cancer is a genetic condition that leads many people to develop c...
More Answers
11 Things Your Doctor Wants You to Know About Colorectal Cancer
11 Things Your Doctor Wants You to Know About Colorectal Cancer11 Things Your Doctor Wants You to Know About Colorectal Cancer11 Things Your Doctor Wants You to Know About Colorectal Cancer11 Things Your Doctor Wants You to Know About Colorectal Cancer
An expert weighs in on the important stuff—screenings, diagnosis, treatment and more.
Start Slideshow
How Effective Is Sigmoidoscopy in Screening for Colon Cancer?
How Effective Is Sigmoidoscopy in Screening for Colon Cancer?

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.