Activated partial thromboplastin time, an indicator of the endogenous coagulation pathway. The normal range is 31-43 seconds, and below 31 seconds is low. The most common causes of low activated partial thromboplastin time are thrombotic disorders, such as cerebral thrombosis, coronary artery disease, and lower extremity venous thrombosis. Also low activated partial thromboplastin time can occur in the state prior to the formation of a thrombus. Therefore, if low activated partial thromboplastin time is present, it is important to go to the hospital for detailed examination, commonly electrocardiogram and coronary angiography, to see if there is coronary artery disease. If coronary artery disease is present, treatment with coronary artery-dilating drugs or stent placement needs to be given. A cranial CT or cerebral angiogram is also needed to look for narrowing of the cerebral arteries. An ultrasound of the veins of the lower extremities should also be done to see if there is any thrombosis of the veins of the lower extremities.