Colorectal cancer (cancer of the colon or rectum) is one of the most common cancers in Singapore. It is also one of the most preventable, because it usually starts as a polyp that can be found and removed years before it turns into cancer.
This guide explains who should be screened, the screening options, what a complete colonoscopy involves, and the questions worth asking about any colonoscopy you have.
Symptoms are not for screening. If you have blood in your stool, a change in bowel habit lasting more than a few weeks, unexplained weight loss, low blood count (anaemia) or ongoing abdominal pain, see a doctor now rather than waiting for a routine screening test.
Why screening works
Most colorectal cancers develop from growths in the lining of the bowel called polyps, especially a type called adenomas. This usually takes many years, often ten or more. During that time there are usually no symptoms.
- Prevention: removing polyps during a colonoscopy stops them from becoming cancer.
- Early detection: cancers found through screening are more often at an early stage, when treatment is simpler and more likely to cure.
Who should be screened, and when
| Your situation | Usual advice |
|---|---|
| No symptoms, no family history | Start at age 45. Either a stool test (FIT) every year, or a colonoscopy every 10 years if it is normal. |
| A parent, brother, sister or child had colorectal cancer | Colonoscopy, usually from age 40, or 10 years before the age your relative was diagnosed, whichever is earlier. Repeat about every 5 years. |
| Several relatives affected, or cancer at a young age in the family | Possible inherited condition, such as Lynch syndrome or familial adenomatous polyposis. Earlier and more frequent colonoscopy, and referral for genetic counselling. |
| Long-standing ulcerative colitis or Crohn’s colitis | Regular surveillance colonoscopy, usually starting about 8 years after symptoms began. |
| Polyps removed before | Follow-up colonoscopy at the interval set from your last report (see below). |
These are general guides. Your own timing depends on your history and should be agreed with your doctor.
The screening options
| Stool test (FIT) | Colonoscopy | |
|---|---|---|
| What it is | A home test that checks a stool sample for tiny amounts of blood | A camera examination of the whole colon under sedation |
| How often | Every year | Every 10 years if normal and complete |
| Preparation | None | Low-fibre diet and a bowel-cleansing drink |
| Finds polyps | Some; many polyps do not bleed | Yes, including small and flat ones when the view is clear |
| Removes polyps | No | Yes, usually in the same session |
| If abnormal | A colonoscopy is needed | Polyps are removed and sent to the laboratory |
FIT kits are available through the national Screen for Life programme; check current eligibility on HealthHub. Other tests, such as CT colonography and blood-based tests, are used in selected cases. An abnormal result from any of them also needs a colonoscopy.
What a complete colonoscopy involves
A colonoscopy is only as useful as it is thorough. Gastroenterology societies in Europe and the United States publish quality standards for screening colonoscopy, and these are the main points.
- Good bowel preparationStool left in the bowel can hide polyps. Taking the cleansing drink in split doses, the evening before and the morning of the procedure, gives a cleaner bowel. Standards expect adequate preparation in at least 90% of procedures. How to prepare.
- Reaching the start of the colonThe scope should reach the caecum, where the colon begins, and this should be confirmed with photographs. Standards expect this in at least 90 to 95% of procedures.
- Enough time lookingPolyps are found while the scope is slowly withdrawn. Standards recommend an average withdrawal time of at least 6 minutes in colonoscopies where nothing is removed.
- Finding adenomasThe adenoma detection rate is the share of screening colonoscopies in which at least one adenoma is found. It is the main measure of colonoscopy quality, because higher rates are linked to fewer cancers developing later. European standards set a minimum of 25%; US standards, updated in 2024, set 35%.
- Removing polyps completelyPolyps should be removed whole where possible and retrieved for the laboratory. Large or difficult polyps may need a planned second procedure, and the site may be marked with ink so it can be found again.
- A clear report and follow-upYou should receive a report with photographs, the laboratory results once ready, and a recommended date for your next colonoscopy.
Questions to ask about your colonoscopy
These are fair questions for any colonoscopy, and the answers should be in your report.
- Was my bowel preparation adequate?
- Was the whole colon examined, up to the caecum?
- Were any polyps found, were they all removed, and what did the laboratory report show?
- When should my next colonoscopy be, and why that interval?
After polyps are removed: when to repeat
| What was found | Usual next colonoscopy |
|---|---|
| Normal, complete colonoscopy | 10 years |
| 1 or 2 small adenomas (under 10 mm) | 7 to 10 years |
| 3 or 4 small adenomas | 3 to 5 years |
| 5 to 10 adenomas, any adenoma 10 mm or larger, or advanced features on the laboratory report | 3 years |
| More than 10 adenomas | 1 year, and consider genetic assessment |
| A large polyp removed in pieces | About 6 months, to check the site |
Based on the 2020 US Multi-Society Task Force recommendations. Intervals assume good bowel preparation and a complete examination; if either was lacking, the colonoscopy may need to be repeated sooner.
Is colonoscopy safe?
Colonoscopy is a common, generally safe procedure. The main risks are bleeding after polyp removal, which is usually minor, and a tear in the bowel wall (perforation), which is rare, in the order of 1 in 1,000 procedures or fewer. Sedation risks are low, and you will be monitored throughout. Tell the clinic about blood thinners, diabetes medicines and allergies beforehand. More on what to expect on the day.
Insurance
Dr Chia is on the specialist panels of AIA, Great Eastern, HSBC Life, Income, Prudential, Raffles Shield and Singlife for Integrated Shield Plans. Coverage for screening, as opposed to investigation of symptoms, varies by plan, so check with your insurer before the procedure. Corporate insurance panels are listed on the clinics page.
Common questions
At what age should I start colorectal cancer screening?
If you have no symptoms and no strong family history, Dr Chia usually recommends starting screening at 45. Singapore’s national programme, Screen for Life, offers stool tests from 50. If a parent, brother, sister or child has had colorectal cancer, screening usually starts earlier, often at 40.
Is a stool test (FIT) enough?
A yearly FIT is a reasonable screening test for people at average risk, as long as it is repeated every year and any positive result is followed by a colonoscopy. It does not remove polyps and can miss some of them. A colonoscopy examines the whole colon and allows polyps to be removed during the same procedure.
My FIT was positive. What now?
Arrange a colonoscopy soon. Most people with a positive FIT do not have cancer, but a positive result should not be ignored or simply repeated.
How often do I need a colonoscopy?
If a complete, good-quality colonoscopy is normal, the next one is usually in 10 years. If polyps are found, the interval depends on how many there were, their size and what the laboratory report shows, and is usually between 1 and 10 years.
Can I have a gastroscopy at the same time?
Yes. Both can be done in one session under the same sedation. Dr Chia will advise whether a gastroscopy is useful for you, for example for stomach cancer screening.
General information only, not a substitute for a consultation. Written and reviewed by Dr Chia Chung King, gastroenterologist, 2026-11-07. Book a consultation.