Causes a Blockage can be summarized as the formation of CLOTS, which are masses of blood cells and proteins that form when too much of these substances are present in the bloodstream. CLOTS can block the flow of blood through the body, leading to serious health complications such as stroke, heart attack, and pulmonary embolism. CLOTS can be caused by a variety of factors, including genetic predisposition, certain medications, and lifestyle factors such as smoking and lack of exercise.