At what age should colonoscopy screening begin for average‑risk adults and for individuals with a first‑degree relative with colorectal cancer or advanced adenoma, multiple affected relatives, or inflammatory bowel disease?

When to Start Colonoscopy Screening

Average-risk adults should begin colorectal cancer screening at age 45 years, with colonoscopy every 10 years or annual fecal immunochemical testing (FIT) as first-tier options, continuing through age 75. 1

Average-Risk Adults

Starting Age

• Begin screening at age 45 for all average-risk individuals using either colonoscopy every 10 years or annual FIT. 1, 2
• The age 45 recommendation is qualified because direct outcome data for this age group remain limited, though modeling studies and rising incidence in younger birth cohorts support earlier initiation. 1
• Screening from age 50-75 carries a strong (Grade A) recommendation with high-quality evidence demonstrating mortality reduction. 1
• African Americans may benefit from screening at age 45 due to higher incidence rates and earlier onset disease, though this is based on weaker evidence. 3, 4

Screening Methods

• Colonoscopy every 10 years and annual FIT are first-tier, equally ranked options. 1, 2, 4
• Second-tier options include CT colonography every 5 years, multitarget stool DNA (FIT-DNA) every 3 years, and flexible sigmoidoscopy every 5-10 years. 1, 2
• Colonoscopy allows simultaneous detection and removal of polyps, while FIT is often preferred in organized population-based screening programs. 2, 4

Stopping Age

• Discontinue routine screening at age 75 if the patient is up-to-date with prior negative tests, particularly a recent colonoscopy. 1, 2
• For ages 76-85, individualize decisions based on life expectancy (>10 years), overall health status, comorbidities, and prior screening history. 1, 2
• Do not screen individuals older than 85 years—mortality risk and colonoscopy complications outweigh any potential benefit. 1, 2

High-Risk Individuals: Family History

First-Degree Relative with CRC or Advanced Adenoma Diagnosed <60 Years

• Begin colonoscopy at age 40 OR 10 years before the relative's diagnosis age, whichever comes earlier. 1, 2, 4
• Repeat colonoscopy every 5 years. 2, 5, 4
• This applies equally if the first-degree relative had an advanced adenoma (≥1 cm, villous features, or high-grade dysplasia) diagnosed before age 60. 2, 5
• Risk is increased 3.26 to 3.8-fold compared to average-risk individuals. 5, 4

First-Degree Relative with CRC or Advanced Adenoma Diagnosed ≥60 Years

• Begin screening at age 40 using average-risk options: colonoscopy every 10 years or annual FIT. 1, 2, 5
• Risk is only modestly elevated (1.8 to 1.9-fold), so 10-year colonoscopy intervals are appropriate. 5

Two or More First-Degree Relatives with CRC at Any Age

• Begin colonoscopy at age 40 OR 10 years before the youngest affected relative's diagnosis, whichever is earlier. 2, 5
• Repeat colonoscopy every 5 years. 2, 5, 4
• Risk is increased 4.2-fold. 5

Second- or Third-Degree Relatives with CRC

• Begin colonoscopy at age 45 and repeat every 10 years. 2, 5
• These relatives do not warrant the same intensive 5-year surveillance as first-degree relatives. 5

High-Risk Individuals: Inflammatory Bowel Disease

• Begin colonoscopy 8-10 years after symptom onset in patients with ulcerative colitis or Crohn's disease with colonic involvement. 3, 6
• Repeat colonoscopy every 1-3 years depending on disease extent, duration, and presence of primary sclerosing cholangitis. 6

High-Risk Individuals: Hereditary Syndromes

Lynch Syndrome (Hereditary Nonpolyposis Colorectal Cancer)

• Begin colonoscopy at age 25 years or 10 years before the youngest affected relative's diagnosis. 3, 6
• Repeat colonoscopy every 1-2 years. 5, 6
• Genetic counseling and testing should be offered when multiple relatives have CRC across generations, especially with early-onset disease (<50 years). 5, 3

Familial Adenomatous Polyposis (FAP)

• Begin screening at age 10-12 years. 3, 6
• Repeat colonoscopy every 1-2 years. 6

Peutz-Jeghers Syndrome

• Begin colonoscopy at age 8 years. 6
• If normal, repeat at age 18, then every 3 years. 6

Critical Pitfalls to Avoid

• Do not wait until age 50 to begin screening if a first-degree relative was diagnosed with CRC at any age—screening must start at age 40 at the latest. 2, 5
• Verify the exact age at diagnosis of affected relatives, as the 60-year cutoff determines whether 5-year or 10-year colonoscopy intervals are required. 2, 5
• Confirm the diagnosis (CRC vs. advanced adenoma) and total number of affected first-degree relatives, as family history information is often incomplete or inaccurate. 5, 3
• Do not use 10-year intervals if a first-degree relative was diagnosed before age 60 or if two or more first-degree relatives are affected—these situations mandate 5-year intervals. 2, 5
• Do not continue screening beyond age 85—harms definitively outweigh benefits. 1, 2
• Consider genetic counseling if multiple relatives across generations have CRC or polyps, especially with onset before age 50, to rule out Lynch syndrome or FAP. 5, 3, 6