And earlier still if you have a family history or certain bowel diseases. From that page:

However, you may need to be tested earlier than 45, or more often than other people, if you have—

Inflammatory bowel disease such as Crohn’s disease or ulcerative colitis.

A personal or family history of colorectal cancer or colorectal polyps.

A genetic syndrome such as familial adenomatous polyposis (FAP)external icon or hereditary non-polyposis colorectal cancer (Lynch syndrome).