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Cytochrome P450 2C19 Genotype (C806T Variant)

Published: August 9, 2026Updated: August 16, 2026

This test checks for a specific genetic variation in the CYP2C19 gene, which affects how your body processes certain medications.

Quick summary

["Understanding your genetic variation may help doctors choose the right medication dose for you."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
66742-8
Short code
CYP2C19 c.806C>T(*17) Bld/T Ql
Synonyms
CYP2C19 c.806C>T(*17) Bld/T Ql
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

Some medications, like those used to treat depression, heart rhythm issues, or certain infections, rely on the CYP2C19 enzyme to work properly. This genetic test identifies whether you have a variant (C806T) that may slow or change how your body processes these drugs.

How the Test Works

A small blood sample is taken to analyze your DNA. The test looks for the C806T mutation in the CYP2C19 gene, which can influence how effectively your body metabolizes certain medications.

What the Results Mean

Results are typically reported as wild-type (normal variant) or heterozygous/mutant (presence of the C806T variant). This information helps healthcare providers tailor treatment plans to avoid potential side effects or drug ineffectiveness.

Common Medications Affected

The C806T variant is linked to variations in metabolism for drugs like clopidogrel (used to prevent blood clots), escitalopram (an antidepressant), and others in the class of medications called pro-drugs.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

CYP2C19 Genotype Test

Frequently asked questions

Your CYP2C19 genotype may affect how well certain medications work or how quickly they leave your body. For example, if you have the C806T variant, you might need a different dose or alternative medication to achieve the same effect.
This test is often recommended before starting certain medications, especially if you have a history of poor drug response or side effects.
Does this test affect my treatment plan?
Yes, your doctor may use the results to adjust your medication dose or choose a different drug that works better with your genetic makeup.
Is this test painful?
No, the test involves a small blood draw, similar to other routine blood tests. Most people find it quick and not overly uncomfortable.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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