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Furosemide and Creatinine, Urine — Furosemide-to-Creatinine Ratio

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

This urine test measures furosemide, a loop diuretic, along with creatinine to help assess drug excretion and kidney response to therapy.

Quick summary

["The result can help clinicians evaluate furosemide exposure and whether the drug is being excreted adequately in urine."]

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

Key facts at a glance

LOINC
35589-1
Short code
Furoate/Creat Ur
Synonyms
Furoate/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 furosemide, a medicine commonly used to remove excess fluid, in a urine sample. Urinary creatinine is measured as well and may be used to calculate a furosemide-to-creatinine ratio.

Why might I need this test?

Clinicians may use this test when monitoring furosemide treatment, particularly if the expected response is uncertain. It can provide information about drug exposure, medication use, urine output, and kidney function.

How is the test performed?

A urine sample is collected and analyzed in a laboratory for furosemide and creatinine. If both results are reported on a compatible basis, the laboratory may calculate the furosemide-to-creatinine ratio.

How do I prepare for the test?

Follow your clinician's instructions about when and how to collect the urine sample, including whether it should be a timed or spot collection. Tell the laboratory if you recently took furosemide or another diuretic, and do not change your dose unless instructed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine furosemide-to-creatinine ratio

Frequently asked questions

What does furosemide do?
Furosemide is a loop diuretic that increases urine production and helps the body remove excess salt and water. It is often used to treat fluid retention and certain cases of heart or kidney disease.
Why is creatinine included with urinary furosemide?
Creatinine provides a way to account for urine concentration. Comparing urinary furosemide with creatinine can make the drug result more useful than an unadjusted urine drug measurement alone.
Does an abnormal result mean my medication is not working?
Not necessarily. Hydration, kidney function, urine output, dose timing, and medication adherence can all affect the result, so the clinician should interpret it alongside your overall condition.
  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