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The Genetics of Warfarin Response

What is warfarin?

Warfarin, also known as Coumadin®, is a medication that is used to prevent blood from clotting, also known as an anticoagulant. Blood clots can block the flow of blood through the body. If blood flow is blocked it can lead to tissue or organ damage.
Coumadin® Warfarin
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Why might different people require different warfarin doses?

Several factors influence the dose of warfarin needed to prevent blood clots without causing dangerous side effects. Genetic variation explains up to 40% of the differences between individuals. The remaining 60% of the variation in warfarin response can be explained by non-genetic factors, including age, weight, gender, race, diet, other medications and smoking status2.

If only genetic variation is taken into account, then in a Caucasian population:
     - 65 out of a 100 are likely to need a higher dose of warfarin (4.5 mg per day or more)
     - 32 out of a 100 are likely to need an intermediate dose of warfarin (2.6 to 4.4 mg per day)
     - 3 out of 100 are likely to need a lower dose of warfarin (2.5 mg per day or less)

Which genes affect warfarin dose requirements?

Some of the variability between individuals in warfarin dosing requirements is due to genetics. VKORC1, CYP2C9, and CYP4F2 are the genes that affect warfarin response the most. The CPMC analyzes these three genes to determine whether you may need a higher, lower or intermediate dose of warfarin. This information may be useful should your doctor prescribe warfarin for you in the future or if you are on warfarin and the best dose for you has not yet been determined.

Are there other factors that can affect how warfarin works?

Many factors affect how your body will respond to a medication. Non-genetic factors include interactions between different drugs you may be taking, other medical conditions you may have, and interactions between drugs and your lifestyle (diet, exercise, smoking, alcohol consumption etc.).

What does the CPMC Test?

The CPMC evaluates 8 variants associated with warfarin response: 6 variants in the CYP2C9 gene, 1 in the VKORC1 gene, and 1 in the CYP4F2 gene. Your personal result will be displayed in the form of a table on the YOUR GENETIC RESULT tab within your personal report. Your result interpretation can be found on a separate YOUR RESULT INTERPRETATION tab.

For More Information?

  1. PubMed Health Summary of Warfarin
  2. Drugs@FDA Warfarin Drug Details
  3. - Warfarin


  1. Kaufman DW, Kelly JP, Rosenberg L, et al. J Am Med Assoc. 2002;287:337–344.
  2. Cavallari LH & Limdi, NA. Curr Opin Mol Ther. 2009 Jun;11(3):243-51.
  3. Johnson JA, et al. Clin Pharmacol Ther. 2011:(4):625-9.
  4. Pautas E, et al.Clin Pharmacol Ther. 2010 Jan;87(1):57-64.
  5. Borgiani P, et al. Pharmacogenomics. 2009 Feb;10(2):261-6.
This report provides information about the way you may react to the drug warfarin (Coumadin®).

Please share this information with your healthcare providers.
If you are taking warfarin, this information may be useful to your doctor.

If you are not currently taking warfarin this information may affect future prescribing decisions.