Coumadin (Warfarin)

Coumadin is a medication prescribed by doctors to prevent blood clots. The ability for the body to clot is called coagulation and therefore to prevent clots is called anticoagulation. People taking anticoagulants usually refer to it as a “blood thinner”, but it actually doesn’t thin the blood. The body’s ability to clot is very complex. There are multiple steps to be able to form a clot and the body does it in a blink of an eye. There are blood tests available to time the body’s ability to clot called prothrombin time (PT) and partial thrombin time (PTT). It acts on the PT and therefore we can measure the effectiveness/ineffectiveness of it with this blood test. Other anticoagulants work off the PTT part of clotting. As I mentioned the clotting process is very complex and has many steps and uses many enzymes or vitamins to complete a clot.

The clotting process begins with the platelet a small disk that contains clotting factors and enzymes. That when released starts a chain reaction. We can halt the reaction at various stages by eliminating the vitamins or enzymes that are used to create the clot. It simply eliminates a key factor in blood clots, vitamin k. By having less vitamin k in the blood then the body is less able to clot. No vitamin k means no clot, but that also means a small cut or bump can kill you. It is why it's a good rat killer. That’s right it is rat poison!

Rest assured the dose that is prescribed will not do any harm, as long as you get your blood checked on a regular basis (usually once a week) and eat a regular balanced diet.

There are recipes on the internet that call themselves a “Coumadin diet”. Be warned such a diet is not recommended by doctors. The essence of the diet is to eliminate or reduce vitamin k. Please remember that such drastic actions in diet can have dire consequences on your health.

It is always a good rule of thumb to consult a doctor prior to any changes in diet. The doctors can refer you to a dietician to help with food choices that help rather than hinder you health.

Drug Interactions:


May increase risk of bleeding by limiting liver metabolism thus having an additive effect in the blood. Limit by <2 grams per day


May increase of bleeding due to antiplatelet and anticoagulant effect. Low dose aspirin is okay.

Nsaids(Advil, Naproxen, Voltaren)

Non steroidal anti-inflammatories may have an increase risk of bleeding if not properly supervised.


may have increased risk of bleeding due to alteration in vitamin K production.

Clarithromycin and Erythromycin

may increase risk of bleeding by altering liver metabolism

Other anitcoagulants (Heparin, Enoxaparin, Fondaparinux)

By taking more than one anticoagulant may increase your risk of bleeding


May increase risk of bleeding by altering liver metabolism thus having more in the blood. For example the Coumadin dose may not be completely gone when the next dose is due (Accumalatory effect)


Limit by <20 mg per day a higher dose may alter liver metabolism and therefore having an increased risk of bleeding

Return from Coumadin to Cardiac Drugs

Return from Coumadin to Heart Disease and Prevention Homepage

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