Colonoscopy can be used for colorectal cancer screening, evaluation of digestive symptoms, investigation of abnormal test results, and monitoring of certain gastrointestinal conditions.

One important advantage is that abnormal growths called polyps can often be identified and removed during the same examination. Some colorectal cancers develop from polyps over time, so finding and removing certain polyps can help prevent cancer.

Why Colonoscopy Screening Matters

Colorectal cancer can develop without noticeable symptoms, particularly during its earlier stages. Screening is designed to identify cancer or precancerous changes before symptoms appear.

The CDC currently recommends that most adults begin colorectal cancer screening at age 45. Adults ages 45–75 are generally included in routine screening recommendations, while decisions for adults ages 76–85 should consider overall health, previous screening, and individual circumstances.

Colonoscopy is one of several accepted colorectal cancer screening approaches.

Other screening options include:

• Annual fecal immunochemical testing (FIT)

• Stool DNA-FIT testing at recommended intervals

• CT colonography

• Flexible sigmoidoscopy

• Other stool-based screening methods

For average-risk adults, the USPSTF lists colonoscopy as a screening option generally performed every 10 years when results and individual circumstances support that interval.

Who May Need Earlier or More Frequent Screening?

The standard screening schedule does not apply equally to everyone.

A healthcare professional may recommend a different approach when a person has factors that increase colorectal cancer risk, such as:

• A personal history of colorectal cancer

• Previous adenomatous or other concerning polyps

• Inflammatory bowel disease such as Crohn's disease or ulcerative colitis

• A strong family history of colorectal cancer

• Certain inherited genetic conditions

• Previous abnormal colorectal screening results

People with increased risk may need screening earlier than age 45 or at shorter intervals. The CDC specifically advises people with increased risk to discuss their screening schedule with a healthcare professional.

Screening Colonoscopy vs. Diagnostic Colonoscopy

A colonoscopy can have different purposes.

Screening colonoscopy

Screening is performed when a person does not have symptoms and the goal is to look for colorectal cancer or precancerous changes.

Diagnostic colonoscopy

A diagnostic examination may be considered when symptoms or an abnormal test require further investigation.

Possible reasons include:

• Persistent changes in bowel habits

• Blood in the stool

• Unexplained gastrointestinal symptoms

• Abnormal stool testing

• Unexplained anemia

• Follow-up of previously identified polyps

• Monitoring certain gastrointestinal diseases

The appropriate evaluation depends on the individual's symptoms and medical history.

Preparing for a Colonoscopy

Preparation is an important part of colonoscopy because the physician needs a clear view of the colon lining.

The colon generally needs to be thoroughly emptied before the examination. Inadequate preparation can make it harder to identify small polyps or other abnormalities and may affect whether the examination needs to be repeated. NCI notes that thorough cleansing of the colon is required before colonoscopy.

Preparation instructions commonly involve several components:

Dietary instructions

The healthcare team may provide specific instructions about what foods and liquids can be consumed before the examination.

Bowel-cleansing preparation

A prescribed bowel-cleansing regimen is used to remove stool from the colon. The exact preparation and timing depend on the medical facility, patient circumstances, and preparation selected.

Medication review

Some medications and supplements may require special instructions before a colonoscopy. These can include medicines that affect blood clotting or certain medications for diabetes and other conditions.

Patients should follow the instructions provided by their healthcare team rather than changing medications independently.

Transportation planning

Because sedation is commonly used for colonoscopy, arrangements for transportation and post-procedure supervision may be required.

What Happens During the Procedure?

A typical colonoscopy involves several stages.

1. Pre-procedure assessment

The medical team reviews health history, medications, allergies, and preparation status.

2. Sedation

Many patients receive some form of sedation or anesthesia to improve comfort during the examination. The type varies according to the facility, procedure, and individual circumstances.

3. Colonoscope insertion

The flexible colonoscope is carefully introduced through the anus and advanced through the rectum and colon.

4. Examination

The camera allows the physician to inspect the intestinal lining for abnormalities such as polyps, inflammation, bleeding sources, or suspicious growths.

5. Polyp removal or biopsy

If appropriate, polyps may be removed and tissue samples may be collected for laboratory examination.

6. Recovery

After the examination, patients are monitored while sedation wears off. Temporary bloating or abdominal discomfort can occur.

What Can a Colonoscopy Detect?

A colonoscopy can help identify a range of abnormalities.

These may include:

• Colorectal polyps

• Colorectal cancer

• Inflamed intestinal tissue

• Sources of gastrointestinal bleeding

• Certain structural abnormalities

• Changes associated with inflammatory bowel disease

Polyps are particularly important because some types can develop into colorectal cancer over time. Screening can identify these growths before they progress.

Understanding Polyps

A polyp is a growth that develops on the inner lining of the colon or rectum.

Not every polyp becomes cancerous. However, certain types have a greater potential to develop into colorectal cancer.

When a polyp is identified, it may be removed and sent to a laboratory for examination. The pathology report can help determine its type and whether additional surveillance is appropriate.

The recommended timing of a future colonoscopy depends on factors such as:

• Number of polyps

• Size of polyps

• Type of polyp

• Pathology findings

• Quality of the examination

• Personal and family history

Colonoscopy Results

Results can vary considerably.

Normal colonoscopy

No significant abnormality may be identified. The next screening interval depends on the person's risk profile and examination findings.

Polyps identified

One or more polyps may be removed for laboratory analysis. Future surveillance depends on the pathology and other factors.

Abnormal tissue

Inflammation, bleeding sources, or other abnormalities may require additional evaluation.

Suspicious growth

A biopsy or removal may be performed, followed by pathology testing. Further evaluation depends on the findings.

It is important to distinguish between a visual finding during colonoscopy and a confirmed diagnosis. Pathology can provide additional information when tissue is collected.

Recovery After Colonoscopy

Recovery is usually focused on allowing the effects of sedation to wear off and monitoring for complications.

Temporary symptoms can include:

• Bloating

• Gas

• Mild abdominal discomfort

• Tiredness

• Temporary changes in bowel movements

Patients should follow the discharge instructions provided by their medical team.

Because sedation can temporarily affect alertness and coordination, patients may be instructed not to drive or perform certain activities for a specified period.

Possible Risks and Complications

Colonoscopy is generally considered an established procedure, but it is not completely risk-free.

Potential complications can include:

• Bleeding

• Perforation of the colon

• Reactions to sedation or anesthesia

• Infection

• Abdominal discomfort

• Cardiovascular or breathing complications related to sedation

The USPSTF identifies bleeding and perforation among potential harms associated with colonoscopy, with some risks increasing with age.

Urgent medical evaluation may be appropriate after a colonoscopy if someone develops severe or worsening abdominal pain, significant bleeding, difficulty breathing, fainting, high fever, or other concerning symptoms.

Colonoscopy and Other Screening Tests

Colonoscopy is not the only way to screen for colorectal cancer.

These intervals come from USPSTF recommendations and apply to average-risk screening populations. Individual recommendations may differ.

One important difference is that colonoscopy allows direct examination of the entire colon and can permit removal of polyps during the same examination. Other screening methods may require a follow-up colonoscopy if an abnormal result is detected.

Recent Colorectal Screening Updates

Current U.S. guidance continues to emphasize starting colorectal cancer screening at age 45 for average-risk adults.

The CDC's June 2026 colorectal cancer screening guidance states that most people should begin screening at 45 and that several screening tests are available.

The USPSTF continues to recommend screening adults ages 45–75 and recommends individualized decisions for adults ages 76–85.

Another important development is increased attention to screening participation. CDC programs continue to focus on improving colorectal cancer screening among adults ages 45–75 because screening can identify precancerous polyps and early-stage colorectal cancer.

Digestive Health and Colorectal Cancer Risk

Screening is only one part of colorectal health.

Risk can be influenced by factors such as:

• Age

• Family history

• Personal medical history

• Certain inherited conditions

• Inflammatory bowel disease

• Tobacco exposure

• Alcohol consumption

• Physical activity

• Body weight

• Dietary patterns

Not all risk factors can be changed, which makes appropriate screening particularly important.

People should discuss personal risk factors with a healthcare professional rather than relying on age alone.

Tools and Resources

Helpful U.S. resources include:

• CDC Colorectal Cancer Screening — current screening information and guidance

• U.S. Preventive Services Task Force — evidence-based screening recommendations

• National Cancer Institute — information about colorectal cancer and screening tests

• Gastroenterology specialists — evaluation and colonoscopy planning

• Pathology reports — information about tissue or polyp findings after removal

The CDC also recommends discussing screening options and preparation requirements with a healthcare professional.

FAQs

1. At what age should colorectal cancer screening begin?

For adults at average risk, current U.S. guidance recommends beginning colorectal cancer screening at age 45. Adults ages 76–85 may need an individualized decision based on overall health, previous screening, and preferences.

2. How often is a screening colonoscopy performed?

For average-risk adults, the USPSTF lists colonoscopy every 10 years as one recommended screening strategy. People with previous polyps, colorectal cancer, certain medical conditions, or increased inherited risk may have different intervals.

3. Why is bowel preparation necessary?

The colon must be adequately cleansed so the physician can see the intestinal lining clearly. Poor preparation can interfere with examination quality and detection of abnormalities.

4. Can polyps be removed during a colonoscopy?

Yes. When appropriate, polyps can be removed during colonoscopy and sent for laboratory analysis. This is one reason colonoscopy can function as both a screening examination and an opportunity to address certain findings during the same procedure.

5. Is colonoscopy the only colorectal cancer screening option?

No. FIT, stool DNA-FIT, CT colonography, flexible sigmoidoscopy, and other approved screening approaches are also available for appropriate populations. The best option depends on individual risk, preferences, preparation requirements, and follow-up considerations.

Conclusion

Colonoscopy is an important tool for examining the colon and rectum, identifying polyps, investigating certain digestive concerns, and screening for colorectal cancer.

Preparation is a major part of the process because a clean colon helps the physician obtain a clearer examination. During the procedure, abnormalities can be identified and, when appropriate, polyps can be removed or tissue samples collected.

For average-risk adults, current U.S. guidance recommends beginning colorectal cancer screening at age 45. Colonoscopy is one available screening strategy, while other tests may also be appropriate depending on individual circumstances.