Colonoscopy How often should I have one?

General rule is 5 years for people over 50,but if some one has strong family history of ca of colone;such as parents brother or sisters died or have ca of colon,or you have symptoms of blood in stool,change of bowel habits;alternate of lose bowel with constipation or previous colonscopy show major abnormalities then will be much shorter for colonscopy;from 1 year to every 6 months,up to your physician to decide.