Symptoms and Signs of Colorectal Cancer

Executive Summary

Colorectal cancer patients are diagnosed based on signs and symptoms. The symptoms and signs appear with early-stage colorectal. Some of the common signs and symptoms of colorectal cancer include abdominal discomfort, bloating, and irregular bowel movements. Other symptoms include a change in bowel habits, dark blood in the stool, constipation, diarrhoea, weight loss, unexplained iron-deficiency anemia, stools that look thinner or narrower than usual, constant tiredness or fatigue, discomfort in the abdomen, consisting frequent gas pains, bloating, cramps and fullness.

Signs and Symptoms of Colorectal Cancer

It is noteworthy that the signs and symptoms of colorectal cancer listed here are the same as those of common conditions that are not cancer, such as Haemorrhoids and IBS. When suspected cancer, these symptoms typically have begun recently, are severe and long-lasting, and change over time. Being careful about the symptom or signs of colorectal cancer may detect cancer early when it has more chances of being treated successfully.

People with colorectal cancer may experience the mentioned symptoms or signs. A symptom can be something that only a person experiencing it can describe and identify, like nausea, fatigue, or pain. A sign is what other people can measure and identify, like a rash, fever, or an elevated pulse. Together, symptom and signs of colorectal cancer can help describe a medical problem. As mentioned, it is also possible that the signs and symptoms detailed below may be caused by a medical condition which may not be cancer, especially for the general symptoms of abdominal discomfort, bloating, and irregular bowel movements ​1,2​.

  • A change in bowel habits like bowel obstruction or bowel perforation
  • Bright red or very dark blood in the stool
  • Constipation, Diarrhoea, or feeling that the bowel does not empty completely
  • Weight loss with no known explanation
  • Unexplained iron-deficiency anaemia, which is a low number of red blood cells
  • Stools that look thinner or narrower than normal
  • Constant tiredness or fatigue
  • Discomfort in the abdomen, consisting frequent gas pains, bloating, cramps and fullness

Talk with the doctor if any of the above symptoms last for several weeks or become more serious. 

Because colorectal cancer can happen in people younger than the suggested screening age and older people between screenings, anyone at any age experiencing these symptoms should visit the doctor to find out if they should have a colonoscopy.


  1. 1.
    Holtedahl K, Borgquist L, Donker GA, et al. Symptoms and signs of colorectal cancer, with differences between proximal and distal colon cancer: a prospective cohort study of diagnostic accuracy in primary care. BMC Fam Pract. Published online July 8, 2021. doi:10.1186/s12875-021-01452-6
  2. 2.
    Adelstein BA, Macaskill P, Chan SF, Katelaris PH, Irwig L. Most bowel cancer symptoms do not indicate colorectal cancer and polyps: a systematic review. BMC Gastroenterol. Published online May 30, 2011. doi:10.1186/1471-230x-11-65