Common symptoms of colorectal cancer can include:

• Constant tiredness or fatigue
• Feeling very tired all the time
• Having nausea or vomiting
• Losing weight with no known reason
• Unexplained iron-deficiency anemia (low number of red blood cells)
• A change in bowel habits
• Diarrhea, constipation or feeling that the bowel does not empty completely
• Stools that look narrower or thinner than normal
• Bright red or very dark blood in the stool
• Discomfort in the abdomen, including frequent gas pains, bloating, fullness and cramps

However, it is important to note that these may also be symptoms of less severe, more common conditions.