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Lamotrigine/Creatinine Ratio, Urine

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

A urine test that measures lamotrigine relative to creatinine, helping clinicians evaluate drug excretion and interpret the result despite differences in urine concentration.

Quick summary

["This calculated urine ratio can help assess how much lamotrigine is being excreted while accounting for urine concentration."]

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

Key facts at a glance

LOINC
87772-0
Short code
lamoTRIgine/Creat Ur Cfm
Synonyms
lamoTRIgine/Creat Ur Cfm
Category
kidney
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
confirm
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What is this test?

This test measures the amount of lamotrigine in urine compared with the amount of creatinine. The ratio is calculated by the laboratory and can provide context that a lamotrigine level alone may not.

Why might I need this test?

Your clinician may use this test to help evaluate lamotrigine use, drug excretion, and the effect of kidney function. It may also help interpret unexpected lamotrigine levels or assess factors such as missed doses and medication timing.

How is the test performed?

A urine sample is collected as directed by your clinician. The laboratory measures lamotrigine and creatinine and calculates their ratio. The result may come from a single collection or a timed collection, depending on the test ordered.

How do I prepare for the test?

Collect the urine exactly as instructed, including any specified collection period. Continue taking lamotrigine as prescribed unless your clinician tells you otherwise, and tell the laboratory about the timing of your last dose.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine Lamotrigine/Creatinine Ratio

Frequently asked questions

What does a urine lamotrigine/creatinine ratio show?
It compares the amount of lamotrigine in urine with creatinine, which is used as an indicator of urine concentration. This helps provide context when interpreting a urine lamotrigine measurement.
Does this test show whether I am taking my lamotrigine correctly?
Not by itself. The result is influenced by dose, dose timing, urine concentration, kidney function, and other factors, so your clinician will interpret it alongside your medication history and blood test results.
Do I need to collect all of my urine for this test?
It depends on the instructions from your clinician. Some tests use a single urine sample, while others require a timed collection. Follow the collection directions provided with the order.
  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