Serum or plasma concentration of carbamazepine (anticonvulsant drug level)
This test measures the amount of carbamazepine, a medication used to control seizures, in your blood. It helps doctors check if your dose is working properly and adjust it as needed.
["Your carbamazepine blood level helps ensure you’re taking the right amount to manage seizures safely."]
Key facts at a glance
- LOINC
- 94855-4
- Short code
- CBZHLAPNL
- Synonyms
- carBAMazepine hypersens geno Pnl Bld/T
- Category
- chemistry
- Sample
- serum
- Container
- EDTA (lavender-top) tube for whole blood; sterile container for tissue specimens
- Units
- N/A
- Ref low
- 4
- Ref high
- 12
- Critical range
- — – 15 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- PCR-based genotyping for HLA-A, HLA-B, and HLA-DRB1 alleles, including HLA-B*15:02 (SJS/TEN risk) and HLA-A*31:01 (DRESS risk)
- CPT
- 81267
- SNOMED
- 426396006
- Specimen volume
- 3-5 mL whole blood; 5 mg minimum tissue
- Stability
- Whole blood stable at room temperature for 7 days; refrigerated for 30 days. DNA extracted from blood stable for years at -20°C or -80°C. Tissue specimens should be frozen at -80°C or stored in preservative.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 72–336 hours
- Order
- routine
Why This Test Is Done
Doctors may order this test if you’re taking carbamazepine to treat epilepsy or nerve pain. It helps monitor whether your medication is at an effective level without causing harmful side effects. This is especially important if you’ve had seizures, are taking other medications, or if your symptoms change.
What to Expect Before the Test
No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw blood. It usually takes a few minutes, and you may feel a slight pinch. If you’re on blood thinners, let your doctor know before the test.
What the Results Mean
Results show how much carbamazepine is in your blood. They help your doctor decide if your dose needs to be adjusted. Low levels may mean your seizures aren’t controlled, while high levels could increase side effects like dizziness or drowsiness.
Possible Side Effects or Risks
While rare, blood tests can sometimes cause bruising, swelling, or a slight reaction at the injection site. If you experience unusual symptoms like rash, fever, or signs of infection after the test, contact your doctor.
Reference range
Therapeutic: 4-12 mcg/mLN/A
No special preparation required. Patient should be informed of genetic testing implications. Genetic counseling may be recommended prior to testing. Informed consent for genetic testing may be required per institutional policy.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
Carbamazepine Level
Frequently asked questions
What does a low or high carbamazepine level indicate?
How often should I get this test?
Can I eat or drink before this test?
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 17, 2026. · Read our editorial policy