Carbamazepine concentration in blood (serum/plasma)
This test measures the amount of carbamazepine, a medication used to treat certain types of seizures and nerve pain, in your blood. It helps your healthcare provider check if your dose is working properly and if you’re at risk of side effects.
["This test helps monitor your carbamazepine therapy and ensure safe dosing."]
Key facts at a glance
- LOINC
- 18270-9
- Short code
- CBZEPOX
- Synonyms
- Carbamazepine EP SerPl-sCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum collection tube or serum separator tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 50
- Critical range
- — – 15 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
- 80299 (unlisted quantitative drug assay, or refer to 80156-80157 for carbamazepine; metabolite may require alternative coding)
- SNOMED
- 395147008 (Carbamazepine-10,11-epoxide measurement)
- Specimen volume
- 1-2 mL of serum
- Stability
- Serum stable at room temperature for 8 hours, refrigerated (2-8°C) for 7 days, frozen (-20°C) for up to 4 weeks. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
Why This Test Is Done
Your doctor may order this test if you’re taking carbamazepine to manage epilepsy, bipolar disorder, or trigeminal neuralgia. It helps assess whether your medication levels are within a safe range and if you need adjustments to avoid toxicity or insufficient effectiveness.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if your blood is drawn early in the morning. Bring a list of all medications, including over-the-counter drugs and supplements, to share with your provider.
How the Test Is Performed
A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a brief sting, but it usually stops quickly. The blood sample is sent to a lab for analysis using a sensitive method to detect carbamazepine.
What the Results Mean
Results are typically reported as a concentration value (e.g., micrograms per milliliter). Your doctor will compare these results to your specific needs and any guidelines for your condition. Very high or very low levels can signal problems that need attention.
Reference range
Therapeutic reference ranges for carbamazepine 10,11-epoxide are not well-established; clinical interpretation should consider the parent drug level, clinical response, and potential toxicity. Active metabolite typically represents 10-50% of parent carbamazepine concentration in patients on monotherapy.N/A
No special patient preparation required. Trough levels are preferred for therapeutic drug monitoring and should be drawn immediately before the next scheduled dose, typically in the morning. Document the time of last dose and sample collection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Carbamazepine levels help prevent toxicity (e.g., dizziness, nausea, or rash) and ensure adequate drug levels for seizure control. Low levels may mean the medication isn’t working as intended, while high levels could indicate poor metabolism or drug interactions (e.g., with other seizure medications or liver enzymes). Regular monitoring is especially important if you have liver disease or take other medications that affect carbamazepine processing.
Short name
Carbamazepine Level
Frequently asked questions
What causes carbamazepine levels to change?
How often should I get this test?
Can I eat or drink before the 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