Epanutin (Phenytoin)
This test measures Epanutin (phenytoin) levels in the blood. It helps ensure therapeutic dosing while avoiding toxicity and side effects.
Turnaround time
1 day
Biomarkers count
1
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Details about Epanutin (Phenytoin)
What is the Epanutin (Phenytoin) Test?
The Epanutin (phenytoin) test measures the concentration of phenytoin in the bloodstream. Phenytoin is an antiepileptic medication commonly used to control seizures and prevent abnormal electrical activity in the brain.
Because phenytoin has a narrow therapeutic range, small changes in dose can lead to sub-therapeutic levels or toxicity. Blood level monitoring is therefore essential to ensure the medication is effective while remaining safe.
This test is routinely used in patients receiving long-term phenytoin therapy or when dosing adjustments are required.
Why do I need a test for Epanutin (Phenytoin)?
You may need this test to confirm that your phenytoin level is within the therapeutic range. Levels that are too low may result in poor seizure control, while high levels can cause serious neurological and systemic side effects.
Monitoring is especially important after dose changes, when starting or stopping other medications, or if symptoms of toxicity or breakthrough seizures occur.
Symptoms and scenarios where testing is recommended:
- Epilepsy or seizure disorders
- Breakthrough seizures
- Suspected medication toxicity
- Dose adjustments or treatment changes
- Long-term antiepileptic therapy
- Drug interaction monitoring
- Liver dysfunction affecting drug metabolism
- Unexplained neurological symptoms
Benefits of the Epanutin (Phenytoin) Test
- Ensures effective seizure control
Confirms therapeutic drug levels. - Prevents medication toxicity
Identifies dangerously high concentrations. - Supports personalised dosing
Accounts for individual metabolism differences. - Monitors long-term antiepileptic therapy
Essential for ongoing treatment safety. - Detects drug interactions early
Phenytoin levels are affected by many medications. - Supports neurological symptom investigation
Helps explain dizziness, confusion or coordination issues. - Guides clinical treatment decisions
Assists neurologists in dose optimisation. - Established standard of care in epilepsy management
Widely used and clinically validated.
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
- Select your nearest UK clinic and book an appointment.
- A clinician or phlebotomist collects a venous blood sample.
- The sample is analysed for Epanutin (phenytoin) concentration.
- Results are delivered securely online.
Option 2 – Home or Hotel Phlebotomy (+£60)
- Book a UK-wide home or hotel visit at a convenient time.
- A trained phlebotomist collects your blood sample on-site.
- The sample is transported to the laboratory.
- Results are uploaded digitally without the need to travel.
Your Results Explained
Low Levels
Low phenytoin levels may result in inadequate seizure control.
This may require dose adjustment or assessment of compliance.
Typical UK therapeutic range: ~40–80 µmol/L (laboratory dependent).
Normal Levels
Levels within the therapeutic range suggest effective and safe dosing.
This supports stable seizure management.
High Levels
Elevated phenytoin levels increase the risk of toxicity.
Symptoms may include dizziness, unsteady gait, confusion, nausea and visual disturbances, and require prompt clinical review.
How It Works
Simple steps to get your results
Book Online
Choose your test online and book in seconds. Select your preferred clinic location or home visit option.
Visit or Test at Home
Attend one of our UK or London clinics, arrange a home nurse visit, or use a finger-prick kit where available.
Get Your Results
Your sample is analysed by accredited UK laboratories, with secure results delivered directly to you.
Take control of your health with London Blood Tests
WhatsApp UsHow to Prepare for Your Test
Follow these guidelines for accurate results
Sample Timing
Where possible, attend your blood test between 7am and 12pm. Please wait until any short-term illness or infection has fully resolved before testing. Avoid intense exercise for 24–48 hours beforehand, as this can affect certain markers.
Fasting & Hydration
Fasting is not always required, but some tests may recommend it. If fasting is advised, avoid food for 8–12 hours before your appointment and drink water only. Stay well hydrated, as this helps with sample collection and accuracy.
Medications & Supplements
Continue prescribed medications unless advised otherwise by your clinician. Avoid vitamin, mineral, or biotin supplements for at least 24–48 hours before your test, as these can interfere with results. If you are unsure about any medication or supplement, please let us know before your appointment.
Hormones & Menstrual Cycle
For hormone-related tests, timing within your menstrual cycle may be important. If relevant, follow any specific guidance provided on your test page.
If you have any questions or special circumstances, our team is happy to advise before your appointment.