Skip to content

Carbamazepine Free Total Concentration in Serum/Plasma

Published: August 9, 2026Updated: August 14, 2026

This test measures the amount of the drug carbamazepine in your blood as it exists freely (not bound to proteins). It helps doctors monitor your dose to ensure it’s working safely at therapeutic levels.

Quick summary

["This test helps adjust your carbamazepine dose to avoid side effects or insufficient treatment."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 14, 2026Editorial policy

Key facts at a glance

LOINC
34545-4
Short code
CRBMFT
Synonyms
carBAMazepine free+tot Pnl SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top (serum) or serum separator tube (SST)
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 LC-MS/MS for free and total carbamazepine quantification
CPT
80156 (carbamazepine, total); 80157 (carbamazepine, free)
SNOMED
387207008 |Carbamazepine measurement| + 278121008 |Free and total panel|
Specimen volume
1-2 mL serum
Stability
Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 30 days. For free carbamazepine, separate serum promptly and freeze if not analyzed within 48 hours.
Hemolysis max
100
Lipemia max
200
Icterus max
25
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test if you’re taking carbamazepine (a medication used to treat seizures, nerve pain, or bipolar disorder) and want to check if your dose is properly balancing effectiveness and safety. Frequent monitoring is especially important if you have kidney issues or take other medications that interact with carbamazepine.

What Does the Result Mean?

Results are not provided with specific numeric ranges here since they depend on your individual dose, health status, and other medications. Your doctor will interpret the result in the context of your treatment plan. Low levels may suggest your dose is too low, while high levels could indicate overdose or poor metabolism.

How Is This Test Performed?

A blood sample is drawn from a vein in your arm. The sample is then tested using a specialized laboratory method (likely immunoassay or chromatography) to measure the free (unbound) carbamazepine concentration in your serum or plasma.

What Should You Expect Before the Test?

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if instructed by your doctor. Wear comfortable clothing and bring any medications you’re currently taking to your appointment.

Reference range

Therapeutic range: Total carbamazepine 4.0-12.0 µg/mL; Free carbamazepine 1.0-3.0 µg/mL. Optimal sampling: trough level drawn immediately before next dose.N/A

Specimen: serum

No special preparation required. Draw specimen as trough level (immediately before next scheduled dose) for accurate therapeutic drug monitoring, typically 2-4 hours post-dose for peak or just before next dose for trough. Document time of last dose and time of specimen collection.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Why It Matters for Your Health

Short name

Free Carbamazepine Level

Frequently asked questions

How often should I get this test?
Your doctor will determine the frequency based on your treatment plan, how long you’ve been taking carbamazepine, and whether you have any health conditions that affect how your body processes the drug. Typically, tests may be done every few weeks or months to adjust your dose as needed.
What are the typical side effects of carbamazepine that might be monitored by this test?
Carbamazepine can cause side effects like dizziness, drowsiness, or gastrointestinal upset. High levels in the blood may also increase the risk of serious side effects, including skin rashes, liver damage, or bone marrow suppression. Your doctor will watch for these and adjust your dose accordingly.
Can diet or other medications affect this test result?
Yes, certain foods, supplements, or other medications (like grapefruit products or certain antibiotics) can interact with carbamazepine and alter its levels in your blood. Always inform your doctor about all medications, herbs, and dietary changes before taking carbamazepine.
  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 14, 2026. · Read our editorial policy