: Carbamazepine, Trough, Serum or Plasma, Mass Concentration
: This test measures the amount of carbamazepine in your blood just before your next dose, helping your care team gauge whether the medicine level is in a safe and effective range.
[": A trough carbamazepine level helps guide dosing so the drug stays effective without reaching potentially harmful levels."]
Key facts at a glance
- LOINC
- 74973-9
- Short code
- CARB
- Synonyms
- carBAMazepine Trough SerPl-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube or SST (serum separator tube); heparinized plasma tubes also acceptable
- Units
- N/A
- Ref low
- 4
- Ref high
- 12
- Critical range
- — – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Immunoassay (e.g., PETINIA, EMIT) or Chromatography (LC-MS/MS)
- CPT
- 80156
- SNOMED
- 4049-9
- Specimen volume
- 1.0 mL serum or plasma
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 4 weeks. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 100
- Lipemia max
- 500
- Icterus max
- 40
- TAT
- 4–24 hours
- Order
- routine
: What This Test Measures
: Carbamazepine is a medication used to treat seizures and certain nerve pain conditions. This test measures the concentration of the drug in your blood, reported as a mass concentration (for example, in micrograms per milliliter). The sample is usually collected from a vein in your arm.
: Why Trough Timing Matters
: The word "trough" means the sample is drawn just before your next scheduled dose, when the drug level is at its lowest in the dosing cycle. Consistent timing makes results easier to compare over time and helps your care team interpret whether your dose is appropriate for you.
: How to Prepare
: Follow your care team's instructions about when to take your last dose relative to the blood draw, and tell them about all other medicines and supplements you use. Do not change your dose on your own based on this test; any adjustment should come from your clinician.
: What the Results Mean
: Results are interpreted together with your dose, the timing of the draw, your symptoms, and other lab values. Levels that are too low may not control symptoms, while levels that are too high can raise the risk of side effects. Your clinician will explain what your specific result means for you.
Reference range
Therapeutic trough: 4.0-12.0 mcg/mLN/A
Collect specimen immediately before the next scheduled dose (trough level). Patient should be at steady-state (typically 5-7 days after initiation or dose change). Fasting is not required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
: Carbamazepine Trough Level
Frequently asked questions
: Do I need to fast for this test?
: Can I take my carbamazepine dose before the blood draw?
: Should I change my dose if my result is outside the usual range?
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