Kirsten Jackson, known as “The IBS Dietitian,” has observed a troubling pattern: individuals neglecting their gastrointestinal issues, with potentially severe consequences.
“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 particularly 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 encountered similar cases where 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 observes in his practice.
Dr. Dianne Pearre has also witnessed this, 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 further underscore these concerns: one in three adults cannot name a single symptom of bowel cancer, even though nearly 1.5 million people in the U.S. live with it.
To help others avoid this and encourage timely treatment before cancer worsens, medical providers share commonly missed signs of bowel cancer, what they are often mistaken for, and when to see a doctor.
Unexplained Weight Loss
While diet culture praises weight loss regardless of cause, it is 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 also mentioned this sign, noting it is often mistaken for stress, diet, or aging. He added that it is 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 ten pounds without trying, or if the weight loss is accompanied by fatigue, anemia, or bowel changes.
Black or Dark Stools
Darker poops are not 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 completely black. According to Pearre, “dark stools” are a common sign of colorectal cancer that are often missed or misattributed.
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 is 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 is another commonly missed sign. In other words, bowel cancer is not 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 does not automatically indicate cancer. “Sometimes, overnight symptoms can also indicate other conditions, like bile acid diarrhea or IBD,” she clarified. It is 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 do not 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.”
