NSK-SD is a powerful enzyme that has demonstrated in clinical trials to support endogenous fibrinolytic activity, thus, dissolving blood clots. This customer favorite, has a long term success rate. NSK-SD is the original Nattokinase formula and is studied extensively in Japan and in the United States. Because this product promotes blood flow and circulation, NSK-SD should not be used by those with bleeding problems. Those using anti-coagulant treatments should consult their doctor before using. Please contact us directly to speak with one of our licensed health professionals for any concerns or questions.