Carbamazepine (Serum/Free Concentration)
This test measures the free (unbound) amount of carbamazepine, a medication used to treat certain types of seizures and nerve pain, in your blood.
["Understanding your free carbamazepine levels helps doctors monitor your medication dose for optimal safety and effectiveness."]
Key facts at a glance
- LOINC
- 14056-6
- Short code
- CBZE
- Synonyms
- Carbamazepine EP Free SerPl-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube or serum separator tube (SST)
- Units
- N/A
- Ref low
- 0.5
- Ref high
- 3
- Critical range
- — – 4 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Liquid chromatography-tandem mass spectrometry (LC-MS/MS) or High-performance liquid chromatography (HPLC)
- CPT
- 80100
- SNOMED
- 395099008
- Specimen volume
- 1.0 mL serum
- Stability
- Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 30 days
- Hemolysis max
- 100
- Lipemia max
- 200
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
Why This Test Matters
Free carbamazepine is the active form of the drug that actually reaches your brain to work. Measuring it helps ensure your dose is neither too high (risking side effects) nor too low (risking seizures).
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your doctor specifies it. Wear a loose shirt for easy access to your arm.
How the Test is Performed
A healthcare provider will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but the procedure is quick and usually painless.
Possible Side Effects or Risks
Most people experience no discomfort beyond the minor bruising or slight soreness at the injection site. Rarely, blood tests can cause allergic reactions or fainting.
Reference range
Therapeutic range: 0.5-3.0 mcg/mL (when co-administered with carbamazepine); levels may vary based on clinical context and individual responseN/A
No special patient preparation required. Specimen should be collected prior to next dose (trough level) for accurate therapeutic drug monitoring.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free carbamazepine levels are critical for patients on this medication because it directly correlates with seizure control and toxicity risk. Low levels may indicate insufficient dosing, while high levels can signal overdose or drug interactions that need adjustment.
Short name
Free Carbamazepine Level
Frequently asked questions
Why might my doctor order this test?
What do my results mean?
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 15, 2026. · Read our editorial policy