How Do Vitamin K & Aspirin React to Each Other?

Aspirin, also called acetylsalicylic acid, has a number of potential therapeutic effects. The drug can manage inflammation, help to control pain, and also has implications in managing some types of cardiovascular disease. Aspirin has an effect on your bloodstream, and can interact with other compounds that control blood clotting, including vitamin K.

One of the primary functions of vitamin K is to control your blood thickness, and allow for blood clotting in case of injury. Vitamin K can activate a number of proteins involved in a cellular communication pathway called a coagulation cascade. This cascade promotes the aggregation of blood cells, called platelets, to cause the formation of a blood clot. Too little vitamin K can prevent your body from properly responding to injury, increasing your risk of bruising and other internal bleeding. Vitamin K also interacts with pharmaceuticals that have an effect on blood clotting, including warfarin and aspirin.

Some individuals who have clotting disorders and face an increased risk of dangerous blood clots take aspirin to help control their blood thickness. Aspirin has the opposite effect of vitamin K, and helps to prevent the improper activation of the coagulation cascade. Depending on the severity of the clotting disorder, patients might take aspirin on its own, or in combination with other anti-coagulant medications.

Aspirin and vitamin K can work in combination to help keep your blood at an appropriate thickness in some, but not all, cases. A proper balance of aspirin and vitamin K allows your body to properly respond to injury, while also preventing spontaneous clot formation. A change in the dosage of your vitamin K or aspirin supplements can disrupt this balance, favoring either bleeding or clot formation. If you take aspirin, tell your doctor which vitamin supplements you take, and notify your doctor of any changes to your supplement regimen.

In some cases, drugs that affect the activity of vitamin K within your body can lead to complications if you also take aspirin. A study published in May 2009 in the "Journal of Thrombosis and Thrombolysis" indicates that vitamin K antagonists -- drugs that decrease vitamin K activity in your body -- do not offer additional advantages over aspirin therapy alone in most cases, and might lead to adverse reactions. If you already take medication to control the activity of vitamin K in your body, always consult a doctor before taking aspirin.