Clotting & bleeding
Dic causes two opposite problems: blood clots when it shouldn't, then abnormal bleeding occurs.
The blood has enzymes to cause clotting--if you have a small cut, the blood clots naturally to help stop bleeding. In dic, abnormal clotting happens; clots form in the small blood vessels all over the body. When all the clotting enzymes get used up, it's a setup for bleeding.