The first signs of colon cancer that patients notice include a change in their stool consistency or bowel habits, or blood in their stool, according to Mayo Clinic. Other signs and symptoms include feeling that the bowel does not empty completely, fatigue or weakness, or weight loss for no reason.
When colon cancer is in its early stages, many people do not experience symptoms, notes Mayo Clinic. Once symptoms appear, they tend to vary in relation to where the tumor is located in the large intestine and its size. Generally, colon cancer screenings are recommended for people age 50 and older, but doctors may recommend the screenings begin sooner in cases of a family history of the disease.