Colon Cancer Symptoms: Early Signs & When to Get Screened

Medically reviewed by Dr. E. Vimalakar Reddy, Surgical Gastroenterologist, Apollo Hospitals, Jubilee Hills, Hyderabad  |  Last reviewed: 24 June 2026

Quick answer: The main symptoms of colon (colorectal) cancer are a lasting change in bowel habits, blood in the stool, abdominal pain or cramping, a feeling that the bowel doesn't empty fully, unexplained weight loss and tiredness. Many cases cause no symptoms early on — so screening from age 45 (earlier with a family history) is the most reliable way to catch it.

Common symptoms of colon cancer

• A change in bowel habits — diarrhoea, constipation or narrower stools — lasting weeks.
• Blood in or on the stool, or black stools.
• Persistent abdominal discomfort — cramps, gas or pain.
• A feeling that the bowel does not empty completely.
• Unexplained weight loss.
• Weakness or fatigue (often from anaemia).

Don't assume it's "just piles"

Rectal bleeding is most often from haemorrhoids, but colon cancer can cause identical symptoms. The only way to be sure is a clinical check and, where needed, a colonoscopy. Self-diagnosing as piles is one of the most common reasons colon cancer is found late.

Who is at higher risk?

• Age 45 and above.
• Family history of colon or rectal cancer or polyps.
• Long-standing inflammatory bowel disease.
• Smoking, heavy alcohol use, obesity and a diet high in red/processed meat and low in fibre.

Related reading

• Early signs of GI cancer
• At what age to start colon cancer screening
• When should you get an endoscopy?

Sources: WHO; ICMR / National Cancer Registry Programme. Disclaimer: For general awareness only; not a substitute for professional medical advice. Consult a qualified doctor about your symptoms.