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Lamotrigine concentration in serum/plasma

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

This test measures the amount of lamotrigine, a medication used to treat epilepsy and certain mood disorders, in your blood.

Quick summary

["Your doctor may check this level to ensure the medication is working safely and at the right dose."]

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

Key facts at a glance

LOINC
59920-9
Short code
lamoTRIgine Gast-sCnc
Synonyms
lamoTRIgine Gast-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84484
SNOMED
302774002
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your healthcare provider may order this test if you’re taking lamotrigine to monitor your response to treatment, check for side effects, or adjust your dose. It helps ensure you’re getting the right amount of medication for your condition.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re on a blood thinner, let your provider know before the test.

What the Results Mean

Results are compared to a general reference range, but your specific range may vary based on your dose and health. Too little or too much lamotrigine can affect your condition or cause side effects.

Possible Side Effects

While rare, very high levels of lamotrigine may cause dizziness, rash, or nausea. Low levels might mean your medication isn’t working as expected. Always discuss symptoms with your provider.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Lamotrigine Level

Frequently asked questions

What happens if my results are out of range?
If your lamotrigine level is too low, your doctor may increase your dose. If it’s too high, they may lower it or switch medications to avoid serious side effects. Always follow their guidance.
Can I eat or drink before the test?
You can eat and drink normally unless instructed otherwise. Some tests require fasting, but this one does not.
How often will I need this test?
Your doctor will determine how often you need testing based on your treatment plan, medication dose, and health status. Follow their schedule for follow-up.
  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