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Fentanyl, Urine — Mass Concentration (Body-Mass/Creatinine Adjusted)

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

A quantitative urine test for fentanyl, reported as an amount per volume and potentially adjusted for body mass and creatinine to help interpret the result.

Quick summary

["This urine test detects and measures fentanyl, but the result alone does not establish whether someone is experiencing toxicity."]

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

Key facts at a glance

LOINC
78766-3
Short code
fentaNYL adj bodymass+crea Ur-mCnc
Synonyms
fentaNYL adj bodymass+crea Ur-mCnc
Category
kidney
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 fentanyl present in a urine sample. Some reports adjust the result using the person's body mass and urine creatinine level to account for differences in urine concentration.

Why might I need this test?

Urine fentanyl testing may be used in pain-management monitoring, medication adherence assessments, substance-use evaluation, or investigation of suspected opioid exposure.

How is the test performed?

A urine specimen is collected and analyzed in the laboratory using a validated quantitative method. The report may show the measured concentration and, when appropriate, a body-mass- or creatinine-adjusted value.

How do I prepare for the test?

Fasting is generally not required. Follow the laboratory's urine-collection instructions, and tell the clinician about fentanyl-containing medicines or other substances you have used, because they can affect interpretation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

A detectable result indicates that fentanyl or its metabolites were present in the urine, but it does not by itself show the current dose, impairment, or severity of toxicity. Urine levels can vary with timing, hydration, metabolism, and drug use. If slowed breathing, extreme sleepiness, or inability to awaken is present after possible fentanyl exposure, seek emergency care immediately.

Short name

Urine fentanyl

Frequently asked questions

Does a positive urine fentanyl test mean I am overdosing?
No. It shows that fentanyl was detected, but the result must be interpreted with symptoms, timing, dose history, and other clinical findings.
Why is my result adjusted for body mass or creatinine?
These adjustments can help account for body size and variations in urine concentration. The exact calculation depends on the laboratory report.
Can a fentanyl urine test miss recent exposure?
Yes. Detection depends on when the sample was collected, how the drug was taken, and how quickly the body eliminates it. A negative result does not completely exclude exposure.
  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