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Carbamazepine concentration (serum/plasma)

Published: August 9, 2026Updated: August 17, 2026

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

Quick summary

["Knowing your carbamazepine levels helps your doctor monitor your dose and ensure it’s working safely."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
73050-7
Short code
CBZ-NAB
Synonyms
carBAMazepine (neut) IgG SerPl Ql FC
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or red-top clot tube; plasma acceptable in EDTA or heparin tube
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
flow-cytometry
CPT
86021
Specimen volume
2 mL serum or plasma
Stability
Stable for 48 hours at 2-8°C; for extended storage, freeze at -20°C or below. Avoid repeated freeze-thaw cycles.
Hemolysis max
100
Lipemia max
100
Icterus max
50
TAT
48–168 hours
Order
routine

Why This Test Matters

Carbamazepine is a prescription drug that works by stabilizing electrical activity in the brain. It’s often prescribed for epilepsy or conditions like trigeminal neuralgia. Your doctor may order this test to check if your dose is effective and to avoid side effects, such as dizziness or drowsiness. Levels can vary based on how your body processes the drug, so regular monitoring is important.

What to Expect Before the Test

No special preparation is usually needed. You may have a small needle inserted into a vein (venipuncture) in your arm, or a blood sample may be taken from a finger. If you’re taking other medications or have health conditions, let your healthcare provider know before the test.

What the Results Mean

Results help your doctor adjust your carbamazepine dose if needed. Too little may mean your seizures or pain aren’t controlled, while too much can cause serious side effects. Your doctor will discuss the results with you and may recommend follow-up tests.

Possible Side Effects

Carbamazepine can cause side effects like dizziness, drowsiness, or stomach upset. Rarely, it may affect blood cells or cause liver problems. If you experience severe symptoms like rash, swelling, or trouble breathing, seek medical attention immediately.

Reference range

Therapeutic: 4-12 mcg/mLN/A

Specimen: serum

No special patient preparation required. Document timing of last carbamazepine dose and onset of neutropenia symptoms on requisition.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Carbamazepine Level

Frequently asked questions

What does my carbamazepine level tell my doctor?
Your carbamazepine level helps your doctor determine if your dose is therapeutic (effective) or if adjustments are needed. Low levels may indicate insufficient medication, while high levels could signal toxicity or improper metabolism. This test is especially important if you’re taking other drugs that interact with carbamazepine, such as certain birth control pills or other seizure medications.
How often should I get this test?
Your doctor will decide how often you need this test based on your treatment plan, how long you’ve been taking carbamazepine, and whether you have other health conditions. Typically, it may be done every few months or as needed to monitor your response.
What if my results are outside the normal range?
If your carbamazepine level is too low, your doctor may increase your dose or switch to a different medication. If it’s too high, they may reduce your dose or investigate potential interactions with other medications you’re taking. Always discuss your results with your healthcare provider to understand what actions, if any, are needed.
  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 17, 2026. · Read our editorial policy