Kirsten Jackson, known as “The IBS Dietitian,” has seen a common trend: People not paying enough attention to their gastrointestinal concerns — and the scary ramifications that can have.
“On numerous occasions, people have self-diagnosed as IBS and skipped over seeing their [doctor] for routine testing, which means they could have missed a [cancer] diagnosis,” she said. “The other thing I am routinely hearing is that people suffer with symptoms for months before seeking help, which is the difference between getting life-saving treatment and a terminal diagnosis if they were to have a cancer diagnosis.”
Mistaking bowel or colorectal cancer for IBS is especially easy since a person can have both conditions. Jackson recalled working with a client who thought their symptoms were just “down to their usual IBS they had had for years.” The patient was later diagnosed with colorectal cancer.
Dr. Andrew Dam, a gastroenterologist at Pomona Valley Hospital Medical Center, has seen similar situations in which patients (and even medical providers) attribute new gastrointestinal symptoms to stress. Attributing serious symptoms to benign conditions is “one of the most concerning patterns” he sees in his practice.
Dr. Dianne Pearre has witnessed this, too, especially in young and otherwise healthy patients. “Almost all of them wished they had sought medical attention sooner,” said the board-certified gynecologic oncologist at The Roy and Patricia Disney Family Cancer Center at Providence Saint Joseph Medical Center in Burbank, California.
Statistics back these concerns up further: One in three adults can’t name a single symptom of bowel cancer, even though almost 1.5 million people in the U.S. live with it.
To help other people avoid this, and to encourage them to get treatment before the cancer worsens, medical providers share commonly missed signs of bowel cancer, what they’re often mistaken as and when to see a doctor.
Unexplained Weight Loss
While diet culture praises weight loss regardless of the cause, it’s not inherently “good” or benign. “People presume they are stressed or not eating enough,” Jackson said. “They overlook it until it becomes quite drastic.”
In fact, unexplained weight loss can be a sign of cancer. Jackson explained that when a person has cancer, their metabolism increases significantly, which can explain the otherwise unexplained weight loss.
Dam mentioned this sign, too, saying it’s often mistaken for stress, diet or aging. He added it’s often the first or an earlier symptom.
“Patients, and sometimes clinicians, may not connect mild weight loss with GI disease, especially if appetite seems normal,” he said. “This is significant because cancer can cause systemic metabolic changes leading to weight loss, even before severe GI symptoms appear.”
He encouraged seeking medical evaluation if you lose more than five to 10 pounds without trying, or if the weight loss is accompanied by fatigue, anemia or bowel changes.
Black Or Dark Stools
Darker poops aren’t necessarily “just from something you ate.”
“Black stools can be a sign of blood from higher up in the gut,” Jackson said.
The stool may not even look totally black. According to Pearre, “dark stools” are a common sign of colorectal cancer that are often missed or misattributed.
Siarhei Khaletski via Getty Images
Rectal bleeding and dark stools could be a sign of underlying disease.
Rectal Bleeding
This symptom can be mistaken for hemorrhoids, especially if the blood is bright red and the patient is younger. While hemorrhoids are common, Dam said, rectal bleeding is also a “classic symptom” of colorectal cancer and “always warrants evaluation,” especially if it’s persistent.
“Patients should see a doctor if the bleeding lasts more than one to two weeks, the blood is mixed within the stool (not just on toilet paper) or if the bleeding is associated with fatigue or anemia,” he said.
To keep it simple, consider rectal bleeding a concern, period.
“If you do experience rectal bleeding, regardless of whether it is bright red or dark, slow or brisk, let your doctor know,” Pearre said. “A quick exam and trial of medical management can determine whether it actually is from hemorrhoids or whether further investigation, such as a colonoscopy, is needed. Even if it isn’t due to cancer treatment, [knowing] the cause of bleeding is necessary.”
Gastrointestinal Changes
Constipation and diarrhea are two scarily common symptoms that can also indicate a person has bowel cancer, especially if the symptoms are new.
“IBS is very common, and symptoms like constipation, diarrhea or alternating patterns overlap heavily with early colorectal cancer,” Dam said. “In colorectal cancer, a tumor can physically alter how stool passes through the colon, leading to new or progressively worsening bowel habit changes.”
You may also experience these “gastrointestinal changes” as unexplained, persistent bloating or pain, Pearre added.
If you experience bowel habit changes after age 45, if the change persists longer than four to six weeks or if you notice a narrowing of stools or incomplete evacuation, Dam urged you to seek medical evaluation.
Pearre agreed. “Appropriate management and timely follow-up for unexplained constipation, diarrhea or bloating can also get you to a colonoscopy and catch cancer promptly,” she said.
Overnight Symptoms
Did your gastrointestinal issues come on suddenly? That’s another commonly missed sign. In other words, bowel cancer isn’t just about symptoms, but the timing of them, too.
“This indicates there is some inflammatory disease process going on because IBS is typically driven by the gut-brain axis, and those symptoms do not appear overnight,” Jackson explained.
To be clear, it doesn’t automatically indicate cancer. “Sometimes, overnight symptoms can also indicate other conditions, like bile acid diarrhea or IBD,” she clarified. It’s still worth getting checked out, though.
Remember: No one wants to think they (or a loved one) would ever get cancer. Denial and even self-gaslighting are normal, but don’t let them negatively affect your health.
“Even if you feel ‘too young,’ current recommendations now support starting colorectal cancer screening at 45 due to rising incidence in younger adults,” Dam said. “Colorectal cancer is often quiet in its early stages, and that’s exactly why it’s missed. The danger isn’t just lack of awareness — it’s misattribution to benign conditions.”
