When to seek medical advice

If you notice any symptoms of colon cancer, such as blood in your stool or a persistent change in bowel habits, see your doctor as soon as possible. Keep in mind that colorectal cancer can occur in younger as well as older people. If you're at high risk, don't wait until symptoms appear. See your doctor for regular screenings.

read more at http://www.mayoclinic.com/health/colon-cancer/DS00035/DSECTION=5