There's one item that's always tucked into your health-checkup notice: that slightly awkward, mildly annoying test where you smear a bit of stool into a small tube and send it off. Its proper name is the fecal occult blood test, and it does exactly what it sounds like, checking whether there's blood mixed into your stool that you can't see with the naked eye. When a small growth or tumor forms in the colon, its surface can get worn and bleed a little, and the whole point of this test is to pick up that blood chemically. I completely get not wanting to do it. But this single sheet acts as the first gate for catching colorectal cancer at a fairly early stage.
Under Korea's national cancer screening program, you're meant to take this test once a year starting at age 50. The "every year" part is the key. It's not that one clean result lets you relax for several years; repeating it on a yearly cycle is what lowers the chance of missing something. Changes in the colon often develop slowly, so even if everything looked fine last year, new bleeding that started this year can be caught. So even if you think "I just did this last year, again?", that's completely normal.
So what happens if the result is positive? This is where a lot of people get a sudden jolt of fear, but blood showing up in your stool absolutely does not mean you have cancer. Hemorrhoids, a small anal tear, something you ate, or menstrual blood mixing in are just a few of the many possible reasons. Still, once occult blood is confirmed, you need to pin down the cause for sure, which is why a colonoscopy is recommended. In truth, the stool test is closer to a first-stage filter that sorts out who needs a scope. If yours comes back positive, the right move is not to put it off but to look directly with a colonoscopy.
There's also the option of starting your screening with a colonoscopy from the outset. With a single colonoscopy, a doctor can look directly inside the colon and, if a polyp is spotted, remove it right there on the spot. That makes it a screening test and a small treatment at the same time. Usually, if the result is clean, you're told to come back in about five years, but if several polyps turned up or they were large, you'll be advised to follow up at shorter intervals. The interval differs from person to person, so it's a good idea to remember the explanation you're given after the exam.
The people who really need to pay attention are a separate group. If a parent or sibling has had colorectal cancer, if you've had inflammatory bowel disease for a long time, or if you've had polyps removed in the past, there's a good chance you should start earlier than the usual age-50 mark and check more often. Also, if your bowel habits suddenly change and your stools become thin, if there's blood in your stool, or if you're losing weight for no reason, this isn't the time to weigh screening intervals; you should just go straight to a clinic. Regular screening is about filtering things out in advance while you have no symptoms, and once symptoms appear, that's a different story.
To sum up: with no particular risk factors, it's a fecal occult blood test every year from age 50, and a colonoscopy if it's positive. If you have a family history or past history, talk it over with your doctor and start earlier. What's written here is only general guidance, so for the schedule that fits your own body, please confirm once more with the place where you get screened.