Bowel cancer often has no symptoms in its early stages [2]. Its common symptoms are blood in the stool (bright red or very dark), a change in bowel habit (diarrhoea, constipation, a feeling of incomplete emptying or stools narrower than usual), ongoing abdominal discomfort such as bloating, wind or cramps, unexplained weight loss and tiredness [5]. Most of these symptoms have a benign cause, but any bleeding or lasting change in bowel habit should be checked by a doctor — at any age.
Key points
- Bowel cancer is the third most common cancer and the second leading cause of cancer death worldwide [1].
- Most of these cancers start from benign polyps; screening can find polyps before they become cancerous [2].
- Screening for people at average risk is recommended from age 45 [3].
- The disease is becoming more common in younger people and is more often diagnosed at a later stage in them [4]; so do not ignore symptoms because you are young.
Symptoms of bowel cancer
| Symptom | Explanation | What to do |
|---|---|---|
| Blood in the stool | Bright red or very dark [5] | Have any new or repeated bleeding checked |
| A change in bowel habit | Diarrhoea, constipation, a feeling that the bowel has not emptied, or narrower or differently shaped stools [5] | If it lasts more than a few weeks, see your doctor |
| Abdominal discomfort | Repeated wind, bloating, fullness or cramps [5] | If it continues, see your doctor |
| Unexplained weight loss | One of the symptoms [5] | See your doctor as soon as possible |
| Tiredness | One of the symptoms [5] | Have unexplained tiredness that persists checked |
| Vomiting | One of the symptoms [5] | Vomiting with abdominal pain and no passing of wind or stool: an emergency |
This table does not replace an examination by a doctor; in most people these symptoms have a benign cause.
The path to diagnosis
- 1
Examination and stool test
A finger examination and a faecal occult blood test are common tests [5].
- 2
Colonoscopy and biopsy
Looking at the bowel with a camera and taking a sample from the suspicious area; the diagnosis is confirmed by testing the sample [2].
- 3
Imaging
CT of the chest, abdomen and pelvis; in rectal cancer, MRI of the pelvis [2].
- 4
Blood and tumour tests
Blood count, liver tests and CEA for the start and follow-up; and MMR/MSI testing on the tumour [6].
When should I call my doctor?
Many people put rectal bleeding down to haemorrhoids and delay seeing a doctor. Although most of these bleeds have a benign cause, any new or repeated bleeding, especially with a change in bowel habit, weight loss or tiredness, should be checked by a doctor, even if you are young.
Severe abdominal pain with vomiting and no passing of wind or stool, or heavy bleeding, needs urgent care at an emergency department.
Related questions
I have blood in my stool; is it definitely piles?
Not necessarily. Blood in the stool can be a symptom of bowel cancer [5], although most cases have a harmless cause. The only way to be sure is an examination by a doctor and, if needed, a colonoscopy.
I am under 45; could I have bowel cancer?
Yes, it is possible. In the United States, the share of all patients who were under 55 almost doubled from 1995 to 2019, reaching 1 in 5 patients [4]. Take symptoms seriously at any age.
Is a CEA blood test enough to diagnose bowel cancer?
No. CEA is not useful for finding cancer in healthy people [7]. Read more: What does a high CEA mean?
What are the screening methods?
From a yearly stool test to a colonoscopy every 10 years; several methods with different intervals are accepted [3]. See: At what age is colonoscopy needed? and If a stool test is positive.
Related cancer types
Related questions
References
7 referencesShow all references, 6 with a study cardClose the reference list
Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
- 1Global cancer statistics 2022: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries
- 2
- 3Screening for Colorectal Cancer: US Preventive Services Task Force Recommendation Statement
- 4Colorectal cancer statistics, 2023
- 5
- 6Localised colon cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up
- 7A Review of the Role of Carcinoembryonic Antigen in Clinical Practice
This page is based on reputable scientific sources and was last updated on 28 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.
Printed from the website; the full and up-to-date version: https://drdabiri.com/en/questions/symptoms-of-colon-cancer/