What is the Carbamazepine (Tegretol) Test?

The Carbamazepine test measures the concentration of carbamazepine, an anticonvulsant and mood-stabilising medication, in the bloodstream. Carbamazepine is commonly prescribed for epilepsy, trigeminal neuralgia and certain mood disorders.

Because carbamazepine has a narrow therapeutic range, blood levels must be carefully monitored. Levels that are too low may result in poor seizure control or symptom relapse, while levels that are too high can lead to serious neurological or systemic side effects.

This test is a standard tool for therapeutic drug monitoring and is used throughout treatment to ensure safe and effective dosing.

Why do I need a test for Carbamazepine?

You may need this test if you are taking carbamazepine and require confirmation that your dose is within the therapeutic range. Individual metabolism varies widely, and carbamazepine can interact with many other medications, altering blood levels unpredictably.

Testing is especially important when treatment is started, when doses are adjusted, if symptoms are not well controlled, or if side effects occur. It is also used in suspected overdose or toxicity.

Symptoms and scenarios where testing is recommended:

• Poor seizure control
• New or worsening side effects
• Dizziness, drowsiness or confusion
• Nausea or vomiting
• Blurred or double vision
• Suspected drug toxicity
• Dose changes or long-term therapy monitoring
• Drug interaction assessment
• Compliance monitoring

Benefits of the Carbamazepine Test

• Ensures therapeutic drug levels
  Confirms medication levels are effective but not toxic.
• Prevents medication toxicity
  Identifies dangerously high carbamazepine concentrations.
• Supports seizure control optimisation
  Helps tailor dosing for epilepsy management.
• Guides dose adjustments safely
  Reduces trial-and-error prescribing.
• Identifies drug interactions
  Detects altered levels due to interacting medications.
• Explains unexplained side effects
  Helps link symptoms to excessive drug exposure.
• Supports long-term treatment monitoring
  Essential for patients on chronic therapy.
• Improves patient safety
  Reduces risk of neurological and systemic complications.

Step-by-Step: How Testing Works

Choose your preferred testing method

You can attend one of our UK partner clinics or arrange a home or hotel visit with a mobile phlebotomist.

Option 1 – In-Clinic Blood Draw

1. Select your nearest UK clinic and book an appointment.
2. A clinician or phlebotomist collects a venous blood sample, usually just before your next dose (trough level).
3. The sample is analysed for carbamazepine concentration.
4. Results are delivered securely online.

Option 2 – Home or Hotel Phlebotomy (+£60)

1. Book a UK-wide home or hotel visit at a convenient time.
2. A trained phlebotomist collects your blood sample on-site.
3. The sample is packaged and transported to the laboratory.
4. Results are uploaded digitally without the need to travel.

Access your report

You can download and share your results with your GP, neurologist or prescribing clinician.

Your Results Explained

Low Levels

Low carbamazepine levels suggest under-dosing or poor absorption.
This may result in reduced seizure control or symptom recurrence.
Typical UK therapeutic range: 4–12 mg/L.

Normal / Therapeutic Levels

Levels within the therapeutic range indicate appropriate dosing.
This suggests effective treatment with reduced risk of side effects.

High Levels

High carbamazepine levels increase the risk of toxicity.
Symptoms may include dizziness, confusion, visual disturbance or cardiac effects.
Dose adjustment or urgent medical review may be required.