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Carbamazepine concentration in serum/plasma

Published: August 9, 2026Updated: August 15, 2026

This test measures the amount of carbamazepine, a medication used to treat certain types of seizures and nerve pain, in your blood.

Quick summary

["Your blood carbamazepine level helps doctors monitor your dose and ensure it’s working safely."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
110766-3
Short code
CARB
Synonyms
carBAMazepine Msmt SerPl
Category
chemistry
Sample
serum
Container
Red-top serum tube (no anticoagulant) or serum separator tube (SST)
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
Immunoassay (e.g., Chemiluminescent Microparticle Immunoassay, EMIT) or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
CPT
80156
SNOMED
1007001002
Specimen volume
1-2 mL of serum (minimum 0.5 mL)
Stability
Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles.
Hemolysis max
500
Lipemia max
100
Icterus max
50
TAT
4–24 hours
Order
routine

Why This Test Matters

Carbamazepine is a prescription drug that helps control seizures and some types of nerve pain. Your doctor may order this test to check if your dose is at a safe and effective level. Too little may mean your symptoms aren’t controlled, while too much could increase risks like dizziness or drowsiness. This test helps balance your treatment to avoid these issues.

How the Test Works

A blood sample is taken from a vein in your arm. The sample is sent to a lab where specialized equipment detects the carbamazepine in your blood. The result is compared to a reference range to determine your level.

What to Expect Before the Test

You can eat and drink normally before the test. Tell your doctor about any other medications you’re taking, as some (like St. John’s Wort) can affect carbamazepine levels. Avoid smoking, as it may also influence results.

What to Expect During the Test

You’ll lie down on a table while a nurse inserts a small needle into your arm to draw blood. It usually takes a few minutes. You might feel a slight pinch, but it’s over quickly. The blood is then sent to a lab for analysis.

Reference range

Therapeutic range: 4.0-12.0 μg/mL (mcg/mL). Optimal seizure control typically occurs within this range; toxicity risk increases above 12 μg/mL.N/A

Specimen: serum

No special patient preparation required. Trough levels should be drawn immediately before the next scheduled dose, typically in the morning, to ensure consistent therapeutic drug monitoring.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Carbamazepine levels help doctors adjust your medication to prevent side effects like dizziness, fatigue, or seizures. Low levels may mean your seizures aren’t controlled, while high levels could indicate toxicity. Regular monitoring is especially important if you’re taking other drugs that interact with carbamazepine, such as certain antibiotics or birth control pills.

Short name

Carbamazepine Level

Frequently asked questions

How often should I get this test?
Your doctor will determine how often you need this test based on your treatment plan, how well your symptoms are controlled, and whether you’re taking other medications that could affect carbamazepine levels. Typically, it may be done every few months or as needed.
What do my results mean?
Results are typically reported as a concentration in micrograms per milliliter (mcg/mL). Your doctor will interpret the result in relation to your symptoms and other health factors. If your level is too high or too low, your doctor may adjust your dose or monitor you more closely.
Can I eat or drink anything before the test?
Yes, you can eat and drink normally before the test. However, inform your doctor about any medications you’re taking, as some may affect the test results.
  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 15, 2026. · Read our editorial policy