Heparin vs. Coumadin

Instructor: Kirstyn Wade

Kirstyn is a registered nurse and has a master's degree in Nursing Education. She has taught college Nursing courses.

Heparin and Coumadin are two widely used anticoagulant medications. In this lesson you will learn more about the similarities and differences between the two medications.

Anticoagulant Medications

Jason has recently suffered from a pulmonary embolism, which is a blood clot in the lung. He is recovering in the hospital and getting ready to be discharged home. His physician is going to prescribe him an anticoagulant medication to continue to take at home. Anticoagulant medications help prevent blood clots. Jason's physician states that he will either send him home on heparin or Coumadin. Not understanding how the medications differ, Jason asks for additional information on each medication.

How Do Anticoagulants Work?

Anticoagulant medications are often called blood thinners. While they do not technically thin the blood, they are used to treat existing blood clots in veins, arteries, and lungs. They also help prevent future blood clots from forming. A blood clot is when certain blood compounds (platelets and plasma proteins called cofactors) clump together and form a semi-solid gel-like mass. When this occurs outside the body over a cut or laceration, a scab forms. When a blood clot forms inside the body, it can block normal blood flow in the veins and arteries or travel to other places such as the lungs or brain. Blood clots inside the body are considered a medical emergency because they can cut off blood flow to arms, legs, or more seriously, the lungs or brain.

Blood clot inside of a vein
Blood Clot

Heparin and Coumadin both work by reducing the normal clotting ability of platelets and plasma in the blood, however, they have different mechanisms of action.


Heparin works by preventing fibrin and thrombin, two plasma proteins, from working correctly. When these cofactors (proteins that work to clot the blood) are are blocked, blood clots cannot form as easily. Heparin cannot dissolve an existing blood clot in the body, but it can prevent it from becoming larger or prevent new clots from forming.

Heparin is usually supplied as an injectable medication. It can be given by intravenous route (directly into a vein), or subcutaneously. Subcutaneous injections are given using a small needle that goes directly under the skin into the layer of fat between the skin and muscle. Most individuals who take heparin outside of the hospital are taught how to administer subcutaneous injections before they are discharged home.

Subcutaneous injection
SubQ injection


Coumadin is a brand name of the medication warfarin. Similarly to heparin, Coumadin also alters the function of certain plasma proteins in the body. Coumadin affects vitamin K, which controls the production of the blood clotting cofactors. When vitamin K cannot function correctly, it prevents these cofactors from being produced in the first place.

Coumadin is supplied as an injectable intravenous medication, subcutaneous medication, or an oral tablet.

Similarities Between Heparin and Coumadin

Because heparin and Coumadin both work by preventing clotting factors from working correctly, individuals should avoid other medications that 'thin the blood'. These include non-steroidal anti-inflammatories (like ibuprofen), aspirin, corticosteroids, or fish oil. Physicians may also suggest stopping an anticoagulant medication for a number of days before any major surgery or dental work to prevent prolonged bleeding.

Individuals taking heparin or Coumadin should NOT drink alcohol or smoke. Alcohol can alter the effect of these medications and cause stomach bleeding. Smoking can increase the risk of blood clots.

Anticoagulants can cause individuals to bleed more easily. Bleeding can occur in any organ in the body, and individuals on anticoagulants should report any signs of internal bleeding to their physician right away. Signs of bleeding include nose bleeds, blood in urine, black or tarry stools, vomiting blood (often looks like dark coffee grounds), or coughing up bloody sputum or phlegm.

Another rare, but serious side effect of anticoagulants is gangrene of the skin. Gangrene involves necrosis, or death of a body tissue. How anticoagulants cause gangrene is still not well understood, but the risk of developing this condition is highest in the first few days of anticoagulant therapy.

Other side effects of anticoagulants include development of a rash, diarrhea, gas and bloating, yellowing of the eyes or skin (jaundice), hair loss, or itching of the feet. This is not a complete list of side effects, and patients should talk with their physician about all side effects depending on which medication they are prescribed.

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