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Thiopurine Methyltransferase (TPMT) Genomic DNA Analysis (Qualitative)

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

This test checks the genetic variation in your TPMT gene, which affects how your body processes certain medications. It helps determine if you may be at higher risk for side effects from drugs like 6-mercaptopurine or azathioprine.

Quick summary

["Understanding your TPMT gene can help prevent serious reactions to specific medications."]

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

Key facts at a glance

LOINC
100663-4
Short code
TPMT gene c.460G>A&c.719A>G Bld Ql
Synonyms
TPMT gene c.460G>A&c.719A>G Bld 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 Matters for Medication Safety

Your TPMT gene influences how efficiently your liver breaks down certain chemotherapy or immune-suppressing medications. Variations in this gene can lead to either too little or too much of the enzyme TPMT, which may cause side effects like bone marrow suppression or increased risk of blood disorders.

How the Test Works

A small blood sample is taken to analyze your DNA for specific mutations in the TPMT gene. The test is qualitative, meaning it only identifies whether you carry certain genetic variants rather than measuring enzyme activity levels.

What to Expect Before the Test

No special preparation is needed for this genetic test. You may have a blood draw at a clinic or lab, similar to other blood tests. If you’re taking medications like 6-mercaptopurine or azathioprine, discuss your results with your healthcare provider before continuing treatment.

What the Results Mean

Results will indicate whether you have normal, intermediate, or low TPMT activity variants. This helps your doctor tailor your medication dose or choose alternative treatments to avoid potential risks.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Managing Medication Risks

Short name

TPMT Gene Test

Frequently asked questions

Will my results affect my current medications?
Yes, if your TPMT gene has variants that reduce enzyme activity, your doctor may adjust your medication dose or switch to a different medication that’s less affected by these genetic differences.
Can this test help with other conditions besides chemotherapy?
Primarily, this test is used for patients on medications like 6-mercaptopurine or azathioprine. However, it can also be relevant for individuals with inherited blood disorders or those undergoing certain cancer treatments.
How long does it take to get results from this test?
Results are typically available within 1 to 2 weeks, depending on the lab and your healthcare provider’s workflow.
  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