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Morphine/Creatinine Ratio, Urine

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

A urine test that measures morphine relative to creatinine, which may help assess morphine exposure while accounting for differences in urine concentration.

Quick summary

["This test can help evaluate morphine exposure, but results should be interpreted with your medical history and other urine tests."]

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

Key facts at a glance

LOINC
58392-2
Short code
Morphine/Creat Ur
Synonyms
Morphine/Creat Ur
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 morphine in urine compared with the amount of creatinine. Creatinine is used as a reference to help account for how concentrated or dilute a urine sample is.

Why might I need this test?

It may be used to monitor morphine exposure or response to pain treatment, assess suspected opioid use, or support toxicology and substance-use evaluations. It may also be ordered when a healthcare professional needs to interpret a urine drug screen.

How is the test performed?

A urine sample is collected and analyzed in a laboratory to measure morphine and creatinine. The laboratory may report the morphine-to-creatinine ratio, along with other findings when appropriate.

How do I prepare for the test?

Follow any instructions provided by your clinician or testing facility. The healthcare professional who ordered the test can explain whether medications, supplements, or other substances should be disclosed before collection.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine morphine-to-creatinine ratio

Frequently asked questions

Does this test show how much morphine is in my body?
It estimates recent morphine exposure by measuring morphine in urine relative to creatinine. It does not directly determine the current drug level in the blood or how a person will respond to morphine.
Why is creatinine included in the result?
Urine can vary greatly in concentration. Comparing morphine with creatinine helps reduce the effect of changes in urine concentration, although hydration and other factors can still influence the result.
Can prescription or other medications affect this test?
Yes. Some opioids and other medicines can produce substances that may be detected as morphine, and medicines such as rifampin can alter how morphine is metabolized. Tell your clinician about all medications and substances used before the test.
  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