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Furosemide (Lasix) Urine Concentration, 24-Hour Collection

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

This test measures the amount of furosemide, a diuretic medication, in your urine over a 24-hour period. It helps assess how well your body is processing and excreting the drug.

Quick summary

["This test helps doctors check if your kidneys are properly removing furosemide from your body."]

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

Key facts at a glance

LOINC
43461-3
Short code
NM Kidney Views W Furosemide+RNC IV
Synonyms
NM Kidney Views W Furosemide+RNC IV
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
nm
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 This Test Is Done

Your doctor may order this test if you’re taking furosemide to manage conditions like high blood pressure, heart failure, or kidney problems. It helps ensure the medication is working as intended and that your kidneys are handling it safely.

What to Expect Before the Test

You’ll need to collect all urine for 24 hours, starting after you wake up the first morning. Store the sample in a refrigerator and return it to your lab or doctor’s office by the next morning. Follow any specific instructions they provide.

How the Test Works

Your urine is tested for furosemide levels. The test measures how much of the drug appears in your urine, indicating how your body is processing it.

Common Reasons for Abnormal Results

Higher-than-normal levels might suggest your kidneys aren’t removing the drug efficiently, possibly due to kidney issues or improper dosing. Lower-than-normal levels could mean the medication isn’t working as expected.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test is critical for monitoring kidney function and drug metabolism in patients on furosemide. Abnormal results may prompt adjustments to medication, hydration, or further kidney evaluations.

Short name

Urine Furosemide (24-hour)

Frequently asked questions

What does a positive or abnormal result mean?
An abnormal result may indicate issues with kidney function or how your body processes the medication. Your doctor will discuss findings with you and may recommend changes to your treatment plan.
How soon will I get my results?
Results are typically available within a few days to a week, depending on your lab. Your doctor will contact you to review them and explain any next steps.
Can I drink alcohol before this test?
Alcohol may affect how your body processes furosemide. Follow your doctor’s instructions—usually avoid alcohol for 24 hours before the test to ensure accurate results.
  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