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Lamotrigine Serum/Trough Concentration (Mass)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of lamotrigine, a medication used to control seizures, in your blood at its lowest point (trough) after dosing. It helps doctors monitor your dose to ensure it’s effective and safe.

Quick summary

["This test helps adjust your seizure medication to avoid side effects or reduce seizures."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
74944-0
Short code
lamoTRIgine Trough SerPl-mCnc
Synonyms
lamoTRIgine Trough SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Is This Test Done?

Your doctor may order this test if you’re taking lamotrigine to manage epilepsy or bipolar disorder. Trough levels are checked to confirm your medication is working properly and at the right dose for your body.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw blood. The process takes about 5 minutes, and you may feel a brief pinch. Rest assured, this is a standard blood draw.

What Happens During the Test?

The blood sample is sent to a lab where it’s analyzed using a sensitive method to measure lamotrigine’s concentration. Results are typically ready within 24–48 hours.

What the Results Mean

Results show your current lamotrigine level. Your doctor will compare this to your usual dose and medical needs to decide if adjustments are needed. Too-low or too-high levels can affect how well the drug works or cause side effects.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Lamotrigine Level (Trough)

Frequently asked questions

Why do doctors check trough levels specifically?
Trough levels capture the lowest point of medication in your bloodstream after repeated doses. This timing is critical because it directly reflects whether your body is absorbing and processing the drug effectively.
What if my results are outside the expected range?
If your level is too low, your doctor may increase your dose. If it’s too high, they may adjust your timing, dose, or medication to avoid risks like rash or toxicity. Always follow their guidance.
Can I eat or drink before this test?
Yes, you can eat and drink normally. This test only requires fasting for standard blood tests if ordered alongside it, but lamotrigine trough levels don’t need fasting.
  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 16, 2026. · Read our editorial policy