Understanding Anticoagulation

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If you received a mechanical heart valve, your physician may prescribe an anticoagulant medication (blood thinner) to prevent blood clots from forming on or around your valve. Anticoagulation levels will be closely monitored by blood tests. Your physician will determine the level of anticoagulant that is right for you based on guidelines and your medical situation.


To maintain proper levels, take your medication as prescribed and follow-up with blood tests as scheduled. The blood tests performed indicate the anticoagulation level of the blood or the prothrombin time test (PT), and the international normalized ratio (INR).  Always wear or carry patient identification with you that indicates the medications you are taking, their dosages, your PT and INR levels, and the fact that you have received a new heart valve. Learn more about getting a patient ID card.

Other medications can affect your anticoagulation level, including over-the-counter products. Food and alcohol also can affect your level.

Before you have any medical procedure, notify your dentist and any other doctors and health care providers that you are on an anticoagulant. Adjustments in your medication may be needed prior to any procedure.

When taking anticoagulant medication, consult your doctor if any of the following occur: 

  • Excessive bruising
  • Excessive bleeding
  • Blood in your urine
  • Bloody or black, tarry stools
  • Unusual nosebleeds
  • Bleeding gums
  • Pregnancy or planned pregnancy
  • Fever or other illness, including vomiting, diarrhea, or infection

Fact vs. Fiction About Anticoagulants

While some people have strong feelings about the risks of anticoagulants, warfarin is one of the most frequently prescribed drugs in the U.S., with more than 17.8 million prescriptions dispensed annually.1 For more information about anticoagulants, read Fact vs. Fiction About Anticoagulants.

1 Leading Prescriptions Dispensed-through all Channels. Chain Drug Review [serial online]. August 30, 1999; 21(14):RX74. Available from TableBase (Responsive database Services, Inc.), Beachwood, OH. Accessed May, 2001.