6 Signs of Colon Cancer You Should Never Ignore
May 12, 2025 By: Cancer Services Team

Content medically reviewed by Jon Reich, MD
Colon cancer is the third most common type of cancer in the U.S. Within the last few decades, the number of people diagnosed with colon cancer has dropped. Colorectal cancer screenings and raising more awareness about the condition have contributed to lower incidences.
Knowing the signs of colon cancer is one of the best ways to detect the condition in an early stage when treatment is most successful.
“Though colorectal cancer usually doesn’t have signs in its earliest stages, it’s still important to know what to look for,” said Dr. Jon Reich, gastroenterologist at Essentia Health. “If you know the signs of colon cancer, you can report them to your provider sooner, get diagnosed faster, and increase your chances of successful treatment.”
What Are the First Signs of Colon Cancer?
Each person’s colon cancer symptoms may appear differently, and some people never have any symptoms. However, for those who experience symptoms, many are related to digestion.
“Colorectal cancer tumors grow in your large intestine, which can impact how you digest food and pass waste,” Dr. Reich said. “It’s important to note that other health conditions can cause symptoms similar to those of colon cancer, so a health care provider is the only person who can evaluate your symptoms and make an accurate diagnosis.”
Here are six signs of colon cancer you should report to your provider.
1. Changes in Bowel Habits
One of the earliest signs of colon cancer is changes in bowel habits, including frequency and consistency. These changes include –
- Regular constipation or diarrhea: Inform your provider if your bowel movements are more frequent or looser than normal.
- Incomplete emptying: When you feel as though you haven’t completely emptied your colon after a bowel movement, you might feel like you have to rush back to the bathroom and go again.
- Unpredictable urgencies: Sudden urges to use the bathroom only to pass small amounts of stool could indicate colon cancer.
- Narrow stools: Stools that come out as thin and ribbon-like could be signs that a tumor is causing a blockage.
2. Bloody Stool
Blood in the stool can appear differently including –
- Bright red blood: Bleeding from the rectum and colon may appear as bright red streaks in your bowel movements.
- Black stools: Stools that look like tar could also indicate blood is present. Sometimes, a tumor in the colon or rectum can bleed into the large intestine and cause your stool to look darker.
Tell your provider right away if you see blood in your stool. Bloody stools aren’t always a sign of cancer. Other conditions, such as hemorrhoids, also cause rectal bleeding. Your health care provider should always assess this symptom to reach an accurate diagnosis.
You may not always be able to see blood in your stool. Often, your provider finds blood through a fecal occult blood test, which can also help diagnose colon cancer.
3. Constantly Feeling Full
A sense of fullness or bloating can be a sign of colon cancer. Tell your provider if your abdomen is swollen or full after eating small amounts of food. Other gastrointestinal conditions like irritable bowel syndrome can present with similar symptoms, so report it to your provider for evaluation.
4. Cramping or Persistent Abdominal Pain
Occasional abdominal discomfort isn't necessarily something to worry about. But if the pain or cramping is persistent, it is worth making an appointment to see your provider. Colon cancer can cause abdominal discomfort and show up as –
- Excessive gas, along with discomfort and bloating
- Pain that gets worse over time. As a tumor grows, it increases pressure and discomfort in the abdomen.
5. Unexplained Weight Loss
Contact your provider if you’re losing weight without changing your diet or activity levels. Unexplained weight loss could also point to colon cancer due to –
- Cancer impacting your metabolism and triggering weight loss
- Colon blockages disrupting your body’s ability to absorb nutrients
- Tumors consuming a lot of your body’s energy and causing a caloric deficiency
6. Fatigue
Fatigue is an extreme state of feeling tired and lacking energy. This tiredness can occur due to blood loss caused by colon cancer, low iron levels due to blood loss, or the cancer's impact on your body. Fatigue itself is not a telltale sign of colon cancer. If you experience extreme, ongoing fatigue that makes everyday activities difficult, consult your provider, especially if you're also noticing other possible signs of colon cancer.
What You Can Do to Help Protect Yourself
You can’t eliminate your risks of getting colon cancer, but there are steps you can take to help lower your chances of developing the condition, including –
Knowing Your Risks and Family History
About 1 in 4 people with colorectal cancer have a family history of the condition. If you have family members with a history of colon cancer, talk to your provider about when’s the best time to get a screening.
Get a Screening
“Colorectal cancer generally progresses slowly, and colorectal cancer screening can detect cancer at its earliest stages, when it’s easier to treat,” Dr. Reich said. “A colonoscopy can also detect precancerous growths, or polyps, in the colon and rectum, and we can remove those during a colonoscopy so they can’t develop into cancer.”
The Centers for Disease Control and Prevention recommends that adults start regular colon cancer screening by age 45 and continue until 75. You may need to get a screening earlier depending on your risk factors, such as having a family history of colon cancer or inflammatory bowel disease.
Make Lifestyle Changes
Increasing your physical activity, reducing processed foods, and quitting smoking can significantly reduce your risk of colon cancer.