The short answer
Changes in bowel habits — such as diarrhea, constipation, or narrower stools — are usually caused by diet, stress, medicines, or infections, not cancer. A change that lasts more than a few weeks, or comes with blood in the stool or weight loss, is worth getting checked for colorectal cancer.
Most changes in bowel habits come from diet, stress, medicines, or infection.
A change lasting more than a few weeks is worth checking.
Blood in the stool or weight loss with it makes checking more important.
Colorectal cancer is very treatable when found early.
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The full explanation.
The simple version
Everyone's bowel habits change from time to time with food, travel, stress, or a stomach bug. This is normal and usually settles. A change that persists for weeks, though, is worth checking — mostly because colorectal cancer is very treatable when found early.
What usually causes changes
Common causes include changes in diet or fiber, dehydration, stress and anxiety, medicines, infections, irritable bowel syndrome, and conditions like hemorrhoids. These often come and go and relate to what you eat or your routine.
When a change is more worth checking
A change in bowel habits is more worth a doctor's look when it lasts more than a few weeks, such as ongoing diarrhea or constipation, thinner (pencil-like) stools, or a feeling that the bowel does not empty — especially with blood in the stool, belly pain, unexplained weight loss, or tiredness.
When to see a doctor
See a doctor about a change in bowel habits that lasts more than a few weeks, or any change with blood in the stool or weight loss. Ask about colorectal cancer screening if you are due — screening catches many cancers before symptoms start.
Words to know
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Common questions
▸Does a change in bowel habits mean cancer?
Usually not. Most changes come from diet, stress, medicines, or infection. A change lasting more than a few weeks is worth checking, though.
▸What change is more worth checking?
Ongoing diarrhea or constipation, thinner stools, or incomplete emptying — especially with blood in the stool, weight loss, or belly pain.
▸How does screening help?
Colorectal cancer screening, such as a colonoscopy or stool test, can find cancer or pre-cancer before symptoms appear, when it is most treatable.
▸What non-cancer conditions cause bowel changes?
Diet changes, stress, medicines, infections, irritable bowel syndrome, and hemorrhoids are common causes.
Questions to ask your doctor
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