When should colonoscopy screening for colorectal cancer begin in an average‑risk adult and what is the recommended interval?

Colonoscopy Screening Intervals for Average-Risk Adults

For average-risk adults, colonoscopy screening should be performed every 10 years starting at age 50 (strong recommendation) or age 45 (qualified recommendation), continuing through age 75 in individuals with negative prior screening. 1, 2

Starting Age and Initial Screening Interval

• Age 50 remains the most evidence-based starting point with strong recommendation and high-quality evidence supporting colonoscopy every 10 years. 1, 2
• Age 45 screening is a qualified/weak recommendation based on rising colorectal cancer incidence in younger birth cohorts (approximately 2.4% per year in adults 20-29 years), but carries lower-quality evidence than age 50 initiation. 1, 2, 3
• The 10-year interval for colonoscopy is classified as a first-tier screening option alongside annual fecal immunochemical testing (FIT), representing the cornerstones of colorectal cancer screening. 1, 2, 4

Surveillance Intervals After Polyp Findings

The interval changes dramatically based on colonoscopy findings:

• If 1-2 small tubular adenomas (<10 mm) are found: repeat colonoscopy in 5-10 years. 5
• If 3-10 adenomas, any adenoma ≥10 mm, adenoma with villous features or high-grade dysplasia, or serrated polyp ≥10 mm: repeat colonoscopy in 3 years. 5
• If >10 synchronous adenomas: repeat colonoscopy in <3 years. 5
• If only small distal hyperplastic polyps (<10 mm): repeat colonoscopy in 10 years. 5
• If nondysplastic serrated polyps <10 mm: repeat colonoscopy in 5 years. 5

Age to Stop Screening

• Stop routine screening at age 75 in patients who are up-to-date with prior negative screening tests, particularly high-quality colonoscopy, or when life expectancy is <10 years. 1, 2, 6
• For ages 76-85, offer colonoscopy only to never-screened individuals after assessing overall health, comorbidities, and ability to tolerate treatment if cancer is detected. 1, 2, 6
• Discontinue all screening at age 86 and older regardless of prior screening history, as overall mortality risk and adverse events from colonoscopy outweigh life expectancy benefits. 1, 2

High-Risk Populations Requiring Different Intervals

• First-degree relative with colorectal cancer: begin colonoscopy at age 40 or 10 years before the youngest affected relative's diagnosis (whichever is earlier), repeating every 5 years. 2, 4, 7
• African American individuals: consider starting at age 45 (weak recommendation) due to higher incidence rates, maintaining the 10-year interval. 1, 3, 4

Critical Implementation Points

• Never perform colonoscopy at intervals shorter than 10 years in average-risk patients with normal findings, as this represents overuse of resources without evidence of benefit. 2
• Any positive result from non-colonoscopy screening tests (FIT, stool DNA, CT colonography) mandates diagnostic colonoscopy regardless of the patient's last colonoscopy date. 2, 6, 3
• Colonoscopy is contraindicated as a screening test in symptomatic patients with alarm symptoms (rectal bleeding, narrowed stools, unexplained weight loss)—these patients require immediate diagnostic colonoscopy regardless of screening intervals. 2, 6

Evidence Quality Considerations

The 10-year interval for colonoscopy in average-risk adults represents a strong recommendation with moderate-to-high quality evidence from the U.S. Multi-Society Task Force, supported by decades of data demonstrating mortality reduction. 1, 4 This contrasts sharply with the age 45 starting recommendation, which carries only qualified/weak recommendation strength. 1, 2, 3