Depends on symptoms . If you have no symptoms like abdominal pain, change in bowel habits or blood and no relatives, then the age is 50. However, the acg recommends african americans start colonoscopy at the age of 45. If you have a first degree relatvie with colon cancer, you should start at age 40 or ten years younger than the affected relative whichever comes first.
Depends. On risk factors. If you are not at increases risk, screening should begin at age 50. Those with a 1st degree relative with a large polyp or cancer <60yo should begin at age 40 or 10yeara before diagnosis. Those with 2 2nd degree relatives with cancer should have earlier screening. Other reasons for earlier screening include ibd and rare polyp or cancer syndromes.