Blood clotting is necessary to help stop bleeding after an injury. However, sometimes blood clots form where they shouldn’t and can spell trouble for your health.  When blood clots form abnormally, they can be dangerous and block a vein or artery.  Blood clots in the veins and arteries increase the risk for heart attacks, strokes, pulmonary embolisms and miscarriages.  Obviously this all depends on where the clot forms.