I’m a gastroenterologist. These 3 colon cancer symptoms fool most people
Most people know to look out for changes in their bowel habits when it comes to colorectal cancer. But some of the disease‘s warning signs can be far less obvious, making them easier to brush off or attribute to everyday life.
With colorectal cancer on the rise in younger adults, doctors are urging people to pay attention to changes in their health that might otherwise go unchecked. The American Cancer Society estimates there will be about 108,860 new cases of colon cancer diagnosed in the United States in 2026.
Once considered a disease that primarily affected older adults, colorectal cancer is increasingly being diagnosed in younger people, with around one in five cases now occurring in adults under 55, according to the Cancer Research Institute.
Dr. Derek Ebner, a gastroenterologist at Mayo Clinic who specializes in colorectal cancer prevention, shared three symptoms he considers among the disease’s “less obvious” warning signs.
1. Light-Headedness
Feeling dizzy, weak or unusually tired may not seem like a symptom that points to the digestive system, but Ebner said it can sometimes be a sign of iron deficiency anemia caused by the disease.
“Colorectal cancers can bleed very slowly, and the blood loss may not be visible in the stool,” he told Newsweek.
As a result, a person may start to feel exhausted after activities that were once routine and experience weakness or light-headedness.
“These symptoms are easy to attribute to stress, poor sleep, aging or being out of shape,” Ebner said. “In some patients, the anemia itself is the first clue that leads to the diagnosis.”
2. Shortness of Breath
Shortness of breath is another symptom that many people would not instinctively connect to colon cancer.
Iron deficiency anemia can develop when the body does not have enough iron, often due to blood loss, according to Mayo Clinic. Without enough iron, the body cannot produce sufficient hemoglobin, the protein in red blood cells responsible for carrying oxygen around the body.
As oxygen levels drop, people may experience fatigue, weakness and breathlessness, particularly during physical activity.
Because these symptoms can develop gradually, they are often attributed to other causes before the underlying issue is identified.
3. A Persistent Feeling of Incomplete Emptying
Colorectal cancer can also affect normal bowel function in ways that may be mistaken for more common digestive problems.
While persistent diarrhea and blood in the stool are well-known symptoms, Ebner said some people experience the sensation that they still need to have a bowel movement even after they have just been to the bathroom.
“Sometimes described medically as tenesmus or incomplete evacuation, this can be mistaken for constipation, hemorrhoids or another benign bowel problem,” he said.
“A persistent new sensation that the bowel is not emptying normally deserves attention.”
When to Speak to a Doctor
Experiencing one of these symptoms does not mean a person has colorectal cancer. Dizziness, shortness of breath and changes in bowel habits can all have a range of causes, many of which are far more common and less serious.
However, any new symptom that persists, worsens or cannot be easily explained is worth discussing with a doctor. Early detection remains one of the most effective tools in treating colorectal cancer, and identifying potential warning signs sooner can help ensure people receive the care they need as quickly as possible.
Contact Newsweek editors on this story: Charlotte Nisbet and Emma Lee-Sang
