Most people should get their first colonoscopy at age 45. Both the U.S. Preventive Services Task Force and the American Cancer Society recommend routine colorectal cancer screening for all average-risk adults starting at that age, continuing through age 75. The starting age was lowered from 50 in response to rising rates of colorectal cancer in younger adults, a shift the American Cancer Society formally recommended in 2018 and the Task Force adopted in 2021.
But “average risk” doesn’t apply to everyone. Family history, inflammatory bowel disease, and certain symptoms can all move that timeline earlier, sometimes significantly.
The Standard Screening Window: Ages 45 to 75
If you have no family history of colorectal cancer, no personal history of polyps or inflammatory bowel disease, and no concerning symptoms, the recommendation is straightforward: start screening at 45 and continue through 75. A colonoscopy with normal results buys you 10 years before the next one is needed. That 10-year interval is based on how slowly most colorectal cancers develop, from small polyp to dangerous growth.
If polyps are found and removed during your colonoscopy, your doctor will recommend a shorter follow-up interval, typically three to five years depending on the number, size, and type of polyps. This isn’t a sign that something went wrong. It simply means you need closer monitoring because your colon has shown it tends to produce these growths.
When Family History Moves the Timeline Earlier
A family history of colorectal cancer or precancerous polyps is one of the most common reasons to start screening before 45. The general rule: begin at age 40 or 10 years before the age your relative was diagnosed, whichever comes first. So if your parent was diagnosed at 42, you’d start at 32.
This applies if you have one first-degree relative (parent, sibling, or child) or two second-degree relatives (grandparents, aunts, uncles) who had colorectal cancer or precancerous polyps. In these cases, colonoscopy is the preferred screening method rather than stool-based tests, and negative results call for repeat screening every five years rather than every ten.
Hereditary conditions like Lynch syndrome or familial adenomatous polyposis carry even higher risk and require their own screening schedules, often starting in the teens or twenties. If multiple family members have had colorectal cancer, especially at young ages, genetic counseling can help determine whether one of these syndromes is involved.
Inflammatory Bowel Disease Changes the Schedule
If you have ulcerative colitis or Crohn’s disease affecting the colon, your colonoscopy schedule follows a different logic entirely. Surveillance colonoscopies should begin eight years after your IBD diagnosis for people with left-sided or extensive ulcerative colitis, or Crohn’s disease involving more than 30% of the colon. After that, repeat colonoscopies happen every one to three years depending on your individual risk level.
If you also have a first-degree relative with colorectal cancer, screening should start either 10 years before the age that relative was diagnosed or eight years after your IBD diagnosis, whichever comes first. And for people who have both IBD and a liver condition called primary sclerosing cholangitis, surveillance colonoscopies should begin at the time of diagnosis and repeat annually.
Symptoms That Warrant a Colonoscopy at Any Age
Screening colonoscopies are for people without symptoms. A diagnostic colonoscopy is a different category altogether, and age guidelines don’t apply. If you’re experiencing certain symptoms, a colonoscopy may be appropriate regardless of how old you are.
The symptoms that most strongly point toward the need for evaluation include rectal bleeding (blood in or on your stool), which carries roughly five times the odds of being associated with colorectal cancer compared to people without bleeding. Iron deficiency anemia, meaning your body’s iron stores are low for no obvious reason, roughly doubles that association. Persistent changes in bowel habits, ongoing diarrhea, and unexplained abdominal pain are also recognized red flags.
These symptoms are common and usually caused by something other than cancer. But they shouldn’t be dismissed, particularly in younger adults who might assume they’re “too young” to worry about colorectal cancer. Rates of early-onset colorectal cancer have been climbing, and delays in evaluation are a known problem.
After Age 75: An Individual Decision
Between ages 76 and 85, the decision to continue screening becomes personal rather than universal. The Task Force notes that the net benefit of screening everyone in this age group is small. Whether it makes sense for you depends on your overall health, life expectancy, and whether you’ve been screened consistently in the past. Someone who has never been screened may benefit more from a colonoscopy at 78 than someone who had a clean result at 72.
After age 85, screening is generally not recommended. At that point, other health conditions are more likely to affect life expectancy than a slow-growing colorectal cancer, and the risks of the procedure itself carry more weight.
What the Procedure Involves
The colonoscopy itself takes 30 to 60 minutes. You’ll be sedated, so you won’t feel pain during the exam and likely won’t remember much of it. The prep, which involves clearing your bowels the day before, is the part most people find unpleasant: you’ll drink a large volume of liquid laxative and need to stay near a bathroom for several hours.
Because of the sedation, you’ll need someone to drive you home. Plan on taking the rest of the day off, as you’re advised not to drive, work, or make important decisions until the sedation fully wears off. Most people feel normal by the next day.
Insurance Coverage for Screening
Under the Affordable Care Act, all Marketplace health plans and many employer plans must cover colorectal cancer screening for adults aged 45 to 75 with no copay or coinsurance, even if you haven’t met your deductible. This applies to preventive (screening) colonoscopies. If your colonoscopy is diagnostic, meaning it was ordered because of symptoms or to follow up on an abnormal test, different cost-sharing rules may apply depending on your plan.