Everyone needs to undergo screening for colorectal cancer and the timing and frequency of screening is determined by the level of individual risk.
For people without risk factors, the "gold standard" for screening is colonoscopy beginning at age 50 years. In general, colonoscopy is repeated every 10 years or less depending on findings. Alternatively, a flexible sigmoidoscopy can be performed every five years with yearly stool occult blood testing beginning at age 50 years.
For people with a family history of colorectal cancer or polyps, colonoscopy should be performed at age 40 or 10 years earlier than the age of the youngest diagnosed relative. Colonoscopy is generally repeated every five years or less depending on findings.
In people with a rare inherited colorectal cancer syndrome, screening begins much earlier in life and is performed more frequently due to a substantially increased risk.