Lower gastrointestinal (GI) bleeding actually is a complication of another condition. What you and your doctor need to figure out is why you are experiencing the bleeding in the first place. After an exam and some tests, your doctor should be able to pinpoint why you have been having lower GI bleeding and treat both the bleeding and the cause. But if you don't seek treatment for lower GI bleeding, there could be some complications. Loss of a small amount of blood over an extended time could lead to anemia, making you feel fatigued and light-headed. Larger amounts of blood lost could lead to shock and loss of consciousness. Blood flow to the brain could be reduced, causing disorientation and weakness. Further, the underlying disease (which could be hemorrhoids, colorectal cancer, diverticular disease, or others) could have serious consequences if untreated.