Colorectal Cancer Screening: FIT Test & Early Detection Guide
📊 Quick facts about colorectal cancer screening
💡 The most important things you need to know
- Screening saves lives: Regular colorectal cancer screening reduces cancer deaths by approximately 33% and can prevent cancer entirely by detecting precancerous polyps
- Simple home test: The FIT test is done at home with a small stool sample - no preparation, fasting, or dietary changes required
- Early detection is key: When colorectal cancer is found early through screening, the 5-year survival rate exceeds 90%
- Positive test doesn't mean cancer: Blood in stool can have many causes; most people with positive tests do not have cancer
- Start at 45: Current guidelines recommend beginning screening at age 45, or earlier if you have risk factors
- Free in many countries: National screening programs in many countries offer free testing to eligible adults
What Is Colorectal Cancer Screening?
Colorectal cancer screening is a medical test designed to detect cancer of the colon or rectum before you have any symptoms. The most common screening method is the fecal immunochemical test (FIT), which identifies hidden blood in your stool - an early warning sign of cancer or precancerous polyps.
Colorectal cancer - cancer affecting the colon (large intestine) or rectum - is one of the most common cancers worldwide. It develops slowly over many years, usually starting as small growths called polyps on the inner lining of the colon or rectum. While not all polyps become cancerous, finding and removing them through screening can actually prevent cancer from developing.
The concept of screening is fundamentally different from diagnostic testing. When you have symptoms like blood in your stool or changes in bowel habits, your doctor performs diagnostic tests to find out what's causing them. Screening, by contrast, is offered to people who feel perfectly healthy and have no symptoms. The goal is to detect problems before they cause noticeable issues - when treatment is most effective and cure rates are highest.
Regular screening has been proven in multiple large-scale studies to significantly reduce deaths from colorectal cancer. The United States Preventive Services Task Force (USPSTF), European Society of Gastrointestinal Endoscopy (ESGE), and World Health Organization all strongly recommend routine screening for average-risk adults. This recommendation is supported by decades of research showing that screening programs save lives.
Why Is Early Detection So Important?
The stage at which colorectal cancer is discovered has a dramatic impact on survival. When cancer is detected at an early, localized stage - before it has spread beyond the colon or rectum - the 5-year survival rate exceeds 90%. However, when cancer has spread to distant organs like the liver or lungs, the 5-year survival rate drops to approximately 14%. This stark difference underscores why screening is so valuable: it gives you the best chance of catching cancer when it's most treatable.
Beyond survival rates, early-stage cancer also means less intensive treatment. Early cancers can often be removed through minimally invasive procedures during a colonoscopy, potentially avoiding major surgery, chemotherapy, or radiation therapy. This translates to better quality of life, faster recovery, and lower healthcare costs.
Types of Screening Tests
Several different tests can be used for colorectal cancer screening, each with its own advantages. The most common include:
- Fecal Immunochemical Test (FIT): A stool test that detects hidden blood using antibodies specific to human hemoglobin. This is the most widely used screening test globally.
- Colonoscopy: A procedure where a flexible tube with a camera examines the entire colon. It can both detect and remove polyps in the same session.
- Flexible Sigmoidoscopy: Similar to colonoscopy but examines only the lower third of the colon.
- CT Colonography (Virtual Colonoscopy): Uses CT imaging to create detailed pictures of the colon.
- Stool DNA Test: Tests stool for both blood and genetic markers associated with cancer.
Why Am I Offered Regular Screening?
You are offered regular screening because colorectal cancer is common but highly preventable when caught early. Screening programs target adults in specific age groups (typically 45-75) because the risk of colorectal cancer increases significantly with age, and regular testing dramatically improves outcomes.
National screening programs exist because colorectal cancer meets all the criteria for a condition where population-wide screening makes sense: it's common enough to be a significant public health concern, it develops slowly enough that there's a window for early detection, effective screening tests exist, and early treatment is much more successful than late-stage treatment.
Age is the single most important risk factor for colorectal cancer in people without other predisposing conditions. The risk increases substantially after age 45, and approximately 90% of all colorectal cancers occur in people aged 50 and older. This is why screening programs typically begin inviting participants around age 45-50 and continue until age 75, when the benefits of screening must be weighed against other health considerations.
The invitation you receive is not because anyone thinks you're sick - quite the opposite. It's offered to healthy people precisely because screening is most valuable when done before symptoms appear. Think of it like a fire alarm: you want it to detect smoke early, not wait until your house is engulfed in flames.
Receiving a screening invitation is routine and does not mean your doctor suspects you have cancer. It simply means you've reached an age where regular checking becomes beneficial. Taking part is always voluntary, and the test is typically provided at no cost through national health programs.
How Does the FIT Test Work?
The FIT test (fecal immunochemical test) detects tiny amounts of blood in your stool that you cannot see with the naked eye. You collect a small sample at home using a provided kit, then mail it to a laboratory for analysis. Results typically arrive within 2-4 weeks.
The fecal immunochemical test has become the cornerstone of modern colorectal cancer screening programs because it's accurate, convenient, and easy to perform at home. Unlike older tests that could be affected by certain foods or medications, the FIT specifically detects human hemoglobin (the protein in red blood cells), making it more precise and requiring no dietary restrictions beforehand.
The science behind the FIT is straightforward but elegant. Colorectal cancers and large polyps often bleed small amounts into the intestinal tract. This blood mixes with stool and can be detected even when present in quantities too small to see or cause any symptoms. By identifying this "occult" (hidden) blood, the FIT serves as an early warning system for problems that would otherwise go unnoticed until they become more serious.
Step-by-Step: How to Take the Test
Taking a FIT test is simple and can be done in the privacy of your own bathroom. Here's what to expect:
- Receive your kit: You'll get a test kit containing a small tube with a collection stick inside, a plastic bag, instructions, and a prepaid return envelope.
- Collect the sample: During a bowel movement, catch some stool on toilet paper, a paper plate, or a collection device. Open the tube and use the attached stick to collect a small amount - just enough to cover the grooved end of the stick.
- Seal and send: Return the stick to the tube, close it securely, place it in the plastic bag, seal the bag, and put everything in the return envelope. Mail it as soon as possible - no postage required in most programs.
You don't need to prepare in any special way before taking the test. Continue eating normally and taking your regular medications. However, if you have bleeding hemorrhoids or are menstruating, wait a few days as this could affect results. The sample doesn't need to be refrigerated but should be mailed promptly.
What the Test Cannot Detect
While the FIT is an excellent screening tool, it's important to understand its limitations. The test detects blood, not cancer directly. Some cancers and polyps don't bleed, or don't bleed at the time you take the test. This is why regular, repeated screening is important - what one test misses, subsequent tests may catch.
Additionally, the FIT cannot identify the source of bleeding. A positive result tells you that blood is present, but not why. This is why anyone with a positive FIT needs a follow-up colonoscopy to examine the colon directly and determine what's causing the bleeding.
What Do the Test Results Mean?
A negative result means no blood was detected - you'll be invited for another test in 1-2 years. A positive result means blood was found and you need a colonoscopy to identify the cause. Most people with positive results do NOT have cancer; blood can come from many sources including hemorrhoids, inflammation, or benign polyps.
Negative Result: No Blood Detected
If your test comes back negative, it means no hidden blood was found in your stool sample. This is reassuring news, but it doesn't guarantee you won't develop cancer in the future. Colorectal cancer and polyps develop slowly, which is why you'll continue to be invited for regular screening every 1-2 years until you reach the upper age limit of the screening program (typically 74-75 years).
A negative result is the most common outcome. Approximately 95-97% of people who participate in screening programs receive negative results. However, if you develop any symptoms between screening tests - such as visible blood in your stool, unexplained changes in bowel habits, persistent abdominal discomfort, or unexplained weight loss - you should contact your healthcare provider regardless of your last test result.
Positive Result: Blood Was Detected
A positive FIT result can be alarming, but it's essential to understand what it actually means. Blood was detected in your sample - nothing more. At this stage, no one knows why the blood is there. While colorectal cancer is one possibility, there are many other, more common explanations.
Common causes of a positive FIT include:
- Hemorrhoids: Swollen blood vessels in the rectum are extremely common and frequently bleed
- Anal fissures: Small tears in the anal lining can cause bleeding
- Polyps: Many polyps are benign (non-cancerous) but may bleed
- Inflammatory conditions: Conditions like colitis can cause intestinal bleeding
- Diverticular disease: Small pouches in the colon wall may occasionally bleed
If your result is positive, you will receive information about scheduling a colonoscopy. This follow-up examination is crucial because it allows doctors to directly visualize your entire colon, identify the source of bleeding, and - if polyps are found - remove them during the same procedure.
Research shows that only about 3-5% of people with positive FIT results are ultimately diagnosed with colorectal cancer. The majority have benign conditions that are either easily treated or require no treatment at all. The colonoscopy provides answers and peace of mind.
Inconclusive or Invalid Results
Sometimes a test cannot be properly analyzed. Common reasons include too much stool on the collection stick, a sample that wasn't returned promptly, or issues with the collection tube. If this happens, you'll receive a new kit to repeat the test. This is not cause for concern - simply follow the instructions carefully and try again.
What Happens After a Positive Result?
After a positive FIT test, you'll be referred for a colonoscopy - a procedure where a doctor uses a flexible camera to examine your entire colon. This is the gold standard for investigating positive screening results and can both diagnose problems and remove polyps in the same session.
A colonoscopy is a detailed examination of the entire large intestine using a colonoscope - a long, flexible tube with a light and camera at the end. The procedure typically takes 30-60 minutes and is performed by a gastroenterologist or trained endoscopist. Most people receive sedation to ensure comfort during the examination.
Preparing for a Colonoscopy
The most challenging part of a colonoscopy for most people is the bowel preparation beforehand. Your colon must be completely clean for the doctor to see clearly. This involves drinking a special solution that causes temporary diarrhea to flush out the bowel contents. While unpleasant, thorough preparation is essential for an accurate examination.
Specific instructions vary, but generally you'll need to:
- Follow a special diet for 1-3 days before the procedure
- Drink the prescribed bowel preparation solution
- Stay near a bathroom as the solution takes effect
- Avoid eating solid food after a certain time
- Arrange for someone to drive you home (due to sedation)
During and After the Procedure
During the colonoscopy, you'll likely be sedated and comfortable. The colonoscope is inserted through the rectum and guided through the entire colon. The doctor carefully examines the intestinal lining, looking for polyps, tumors, inflammation, or other abnormalities. If polyps are found, they can usually be removed immediately using instruments passed through the colonoscope - this is called a polypectomy.
After the procedure, you'll rest until the sedation wears off, typically 30-60 minutes. You may feel bloated or have mild cramping from the air used to expand the colon during the examination. Most people can eat normally and return to regular activities the next day. Your doctor will discuss the findings and any next steps before you leave.
Who Should Get Screened?
Adults aged 45-75 with average risk should undergo regular colorectal cancer screening. People with higher risk factors - including family history of colorectal cancer, inflammatory bowel disease, or certain genetic syndromes - may need to begin screening earlier and have more frequent examinations.
Screening recommendations are designed to balance benefit and risk for different populations. The majority of colorectal cancers occur in people without any specific risk factors other than age, which is why universal screening for average-risk adults is so important.
Average Risk Screening (Ages 45-75)
If you have no particular risk factors for colorectal cancer, current guidelines recommend beginning screening at age 45. This represents a change from previous recommendations that started at 50, reflecting increasing rates of colorectal cancer in younger adults observed over the past two decades.
For average-risk individuals, acceptable screening options include:
- FIT test: Every 1-2 years
- Colonoscopy: Every 10 years (if normal)
- Flexible sigmoidoscopy: Every 5 years
- CT colonography: Every 5 years
- Stool DNA test: Every 1-3 years
Higher Risk Groups
Certain factors increase colorectal cancer risk and may warrant earlier or more intensive screening:
| Risk Factor | Recommended Action | Screening Start Age |
|---|---|---|
| First-degree relative with CRC | Colonoscopy preferred | Age 40 or 10 years before relative's diagnosis |
| Inflammatory bowel disease | Regular colonoscopy surveillance | 8-10 years after disease onset |
| Lynch syndrome | Annual colonoscopy | Age 20-25 |
| Familial adenomatous polyposis | Annual colonoscopy | Age 10-12 |
When Screening May Not Be Appropriate
Screening is not recommended in certain circumstances:
- You have symptoms: If you have blood in your stool, changed bowel habits, or abdominal symptoms, you need diagnostic testing, not screening
- You're already under surveillance: If you're having regular colonoscopies due to previous polyps or cancer, continue that schedule rather than FIT testing
- Serious health conditions: If other health issues mean you wouldn't benefit from or couldn't undergo treatment if cancer were found, screening may not be appropriate
When Should You Contact a Healthcare Provider?
Contact your healthcare provider if you have visible blood in your stool, persistent changes in bowel habits, unexplained weight loss, ongoing abdominal discomfort, or unusual fatigue - even if your last screening test was negative. These symptoms require evaluation regardless of screening status.
Screening tests are designed to detect problems in people without symptoms. If you develop symptoms, you should not wait for your next scheduled screening - seek medical evaluation promptly. The presence of symptoms changes the situation from "screening" to "diagnostic investigation."
Symptoms That Require Medical Attention
Contact a healthcare provider if you experience:
- Visible blood in stool: Whether bright red or dark/tarry
- Changed bowel habits: Persistent diarrhea, constipation, or narrowing of stool
- Unexplained abdominal discomfort: Cramping, pain, or bloating that doesn't go away
- Unintentional weight loss: Losing weight without trying
- Feeling of incomplete bowel emptying: Persistent sensation that your bowel doesn't empty completely
- Unexplained fatigue or weakness: Could indicate blood loss and anemia
- Mucus in stool: Especially if persistent or associated with other symptoms
You have significant rectal bleeding, severe abdominal pain, inability to pass stool or gas, or signs of anemia (extreme fatigue, dizziness, pale skin). These symptoms may require emergency evaluation. Find your emergency number →
How Effective Is Screening?
Colorectal cancer screening is highly effective. Multiple large-scale studies show that regular screening reduces colorectal cancer deaths by approximately 33%. Screening also prevents cancer by detecting and removing precancerous polyps before they become malignant.
The effectiveness of colorectal cancer screening is supported by robust scientific evidence from randomized controlled trials involving hundreds of thousands of participants. These studies consistently demonstrate that screening saves lives - not just by detecting cancer early, but also by preventing cancer from developing in the first place through polyp removal.
Evidence Supporting Screening
Key findings from research include:
- Mortality reduction: Regular fecal occult blood testing reduces colorectal cancer deaths by 15-33%, depending on the study and screening interval
- Incidence reduction: Screening with colonoscopy reduces colorectal cancer incidence by up to 68% through polyp removal
- Stage shift: Screening detects cancers at earlier stages, when treatment is more successful
- Cost-effectiveness: Screening programs are cost-effective and often cost-saving when considering the expense of treating advanced cancer
The Power of Prevention
Perhaps the most remarkable aspect of colorectal cancer screening is its preventive potential. Unlike most cancer screening programs that can only detect disease, colorectal screening can actually prevent cancer. When precancerous polyps are found during colonoscopy, they're typically removed immediately. This simple procedure stops those polyps from ever becoming cancer.
Studies suggest that colonoscopy with polypectomy (polyp removal) reduces colorectal cancer risk by 76-90% in the area examined. This prevention benefit is unique to colorectal cancer and represents a powerful argument for participating in screening programs.
Frequently Asked Questions
Medical References & Evidence Base
This article is based on peer-reviewed medical research and official guidelines from recognized medical organizations. All information follows the GRADE evidence framework and has been reviewed by medical specialists.
Primary Guidelines
- US Preventive Services Task Force. Screening for Colorectal Cancer: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;325(19):1965-1977. doi:10.1001/jama.2021.6238
- European Commission Initiative on Colorectal Cancer. European guidelines for quality assurance in colorectal cancer screening and diagnosis. Endoscopy. 2019.
- World Health Organization. WHO Guide to Cancer Early Diagnosis. Geneva: World Health Organization; 2017.
- Rex DK, Boland CR, Dominitz JA, et al. Colorectal Cancer Screening: Recommendations for Physicians and Patients From the U.S. Multi-Society Task Force on Colorectal Cancer. Gastroenterology. 2017;153(1):307-323.
Systematic Reviews
- Hewitson P, Glasziou P, Watson E, et al. Cochrane systematic review of colorectal cancer screening using the fecal occult blood test (hemoccult). Cochrane Database of Systematic Reviews. 2007.
- Lin JS, Perdue LA, Henrikson NB, et al. Screening for Colorectal Cancer: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA. 2021;325(19):1978-1998.
Evidence Quality
Evidence Level: 1A (Systematic reviews and meta-analyses of randomized controlled trials)
Guideline Organizations: US Preventive Services Task Force (USPSTF), European Society of Gastrointestinal Endoscopy (ESGE), World Health Organization (WHO), American Cancer Society (ACS)
About Our Medical Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, consisting of licensed healthcare professionals with expertise in gastroenterology, oncology, and preventive medicine.
Our team includes board-certified gastroenterologists and oncologists with clinical experience in colorectal cancer screening, diagnosis, and treatment.
All content follows the GRADE evidence framework and is based on current clinical guidelines from USPSTF, ESGE, WHO, and other leading medical organizations.
iMedic has no commercial funding and accepts no pharmaceutical industry sponsorship. Our content is created solely for educational purposes and to promote public health.