Bowel cancer is usually a slow-growing cancer. There are often no symptoms in the early stages of the disease. 

The most common symptoms of bowel cancer are: ^[12][13]

• blood in the stools; this might be bright red if the bleeding is in the rectum, or might make the stools look dark brown or black if the bleeding is somewhere else in the digestive tract 
• a change in bowel habit (loose stools, constipation or stools that are narrower than usual) 
• a feeling that you need to have a bowel movement even after you have had one 
• abdominal pain, cramping or bloating 
• vomiting 
• weight loss 
• unexplained tiredness or fatigue. 

The first sign of bowel cancer is sometimes a blood test showing a low red blood cell count, as a result of bleeding into the digestive tract. ^[14]

Many conditions can cause these symptoms, not just bowel cancer. If you have any of these symptoms, talk to your doctor. Bleeding from the rectum should never be ignored.