Colon Cancer is Rising in Adults Under 40: Symptoms You Should Never Ignore

For years, colon cancer was considered a disease of older adults. But that’s no longer the case. More adults under 40 are being diagnosed, and many are in later stages when treatment is harder. 

The good news? When caught early, colon cancer is highly treatable. In fact, the five-year survival rate for early-stage colon cancer is over 90%. However, the key is recognizing symptoms and getting tested as soon as possible. The longer cancer goes undiagnosed, the more it can spread, making treatment more difficult and reducing survival rates. 

Why more young adults are being misdiagnosed 

Because colon cancer has traditionally been rare in younger adults, many doctors don’t immediately consider it. Patients in their 30s and 40s often report that their symptoms were mistaken for common digestive issues like hemorrhoids, irritable bowel syndrome (IBS), or stress-related problems. 

This can lead to delays in diagnosis, allowing the cancer to advance. Some younger patients may have to push their doctors to order tests like colonoscopies or stool screenings. Advocate for yourself if you experience ongoing symptoms and aren’t getting answers. 

Symptoms you should never ignore 

Colon cancer symptoms can be easy to miss or mistaken for common stomach issues. Pay attention to: 

• Changes in bowel habits that last more than a few days, like diarrhea or constipation 
• Blood in your stool or bleeding from the rectum 
• Unexplained weight loss 
• Ongoing stomach pain, cramping, or bloating 
• Feeling like you can’t fully empty your bowels 
• Fatigue or weakness that won’t go away 

If you have any of these symptoms, talk to a doctor. Even if you’re young and otherwise healthy, getting checked could make all the difference. 

When a colonoscopy is recommended 

A colonoscopy doesn’t just help find cancer—it can actually help prevent it. During the procedure, doctors look for small growths called polyps in the colon. Most polyps are harmless, but some can slowly turn into cancer over time. If polyps are found, they can be removed right away, stopping them before they have a chance to become dangerous. While colon cancer is more common in older adults, polyps can show up in younger people too. That’s why screening is so important—it’s not just about finding cancer early, but also about preventing it from ever starting. 

Why more young adults are getting colon cancer 

Doctors don’t fully know why cases are rising in people under 40. But several risk factors may play a role, including: 

• Diet – Eating lots of processed meats, red meat, and low-fiber foods may increase risk. 
• Obesity – Extra weight, especially around the belly, is linked to higher cancer rates. 
• Lack of exercise – Being inactive may lead to inflammation, which plays a role in cancer development. 
• Gut health – Changes in gut bacteria may contribute, though more research is needed. 
• Family history – If a parent or sibling had colon cancer, your risk is higher. 

What you can do now 

Even if you’re not yet 45 (the usual screening age), there are steps you can take: 

• Eat a healthy diet with fiber-rich foods like fruits, vegetables, and whole grains 
• Stay active—even a 30-minute walk a day helps 
• Limit processed and red meats and choose lean proteins 
• Know your family history and tell your doctor if colon cancer runs in your family 
• Don’t ignore symptoms—get checked if something feels off 

Colon cancer is treatable when caught early. If you’re experiencing symptoms, don’t wait. Speak with a doctor and take control of your health today. 

Dr. Sarah Himmelstein is a board-certified general surgeon at Foundation Surgery of Southern New Hampshire Medical Center. Dr. Himmelstein specializes in minimally invasive surgery, hernia repairs, minor procedures, wound care, and screening colonoscopies.