Cytochrome P450 2C9 Phenotype (Genetic Test for Warfarin Metabolism)
This test checks your genetic makeup to determine how your body processes the blood thinner warfarin. It helps doctors choose the safest and most effective dose for you.
["Your genetic makeup affects how well warfarin works to prevent blood clots."]
Key facts at a glance
- LOINC
- 54451-0
- Short code
- CYP2C9 & VKORC1 Bld/T-Imp
- Synonyms
- CYP2C9 & VKORC1 Bld/T-Imp
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- molgen
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Doctors may recommend this test if you’re prescribed warfarin, a medication used to prevent blood clots in conditions like atrial fibrillation, deep vein thrombosis, or after certain surgeries. Genetic variations in the CYP2C9 gene can affect how your liver breaks down warfarin, so knowing your genotype helps prevent bleeding or clotting risks.
How the Test Works
A small blood sample is taken from your arm. The DNA in your blood is analyzed to check for specific variations (mutations) in the CYP2C9 gene that influence how your body processes warfarin. This test does not measure warfarin levels in your blood but helps predict how your body will respond to the medication.
What to Expect Before the Test
No special preparation is needed. You may have a slight bruise or soreness at the site where the blood is drawn, but this usually goes away quickly. If you’re on warfarin, your doctor may adjust your dose based on the results.
What the Results Mean
Results show whether you have common genetic variations in the CYP2C9 gene. These variations can make warfarin more or less effective. For example, certain mutations may require lower doses to avoid excessive bleeding, while others may need higher doses to prevent clots. Your doctor will use these results to tailor your warfarin dose for safety and effectiveness.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
Warfarin Metabolism Genotype
Frequently asked questions
What does this test measure?
How might my results change my treatment?
Can I still take warfarin if I have these genetic variations?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy