MD here. A lot of misinformation in these responses. Red blood is not only from close to the anus. Bright red blood (hematochezia) is generally associated with lower GI origin, which includes all of the colon. And it is definitely one of the presenting symptoms of colon cancer.

Yes, it is also associated with hemorrhoids. And in a 20 year old, that it a higher on the differential. But it should still be checked out. Which means a visit where someone actual does an exam and confirms you have hemorrhoids, or an additional workup (e.g. colonoscopy) if no hemorrhoids are detected. There are other explanations for bleeding that may be common in younger people, and also associated with irregular bowel habits, such as inflammatory bowel disease (Crohn's and ulcerative colitis). And if I saw a 20 year old with irregular bowel habits, bleeding and abdominal pain, that would be my working diagnosis. A colonoscopy will work to evaluate for that, as well.

Bottom line: If you are having bleeding associated with bowel movements, do not write it off.