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Creatinine, Urine-to-Serum Ratio

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

This test compares creatinine levels in urine and blood to help assess kidney filtration, urine concentration, and hydration.

Quick summary

["The result is interpreted alongside other kidney tests because hydration and urine concentration can affect the ratio."]

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

Key facts at a glance

LOINC
59189-1
Short code
MEK/Creat Ur-sRto
Synonyms
MEK/Creat Ur-sRto
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 compares the amount of creatinine in urine with the amount in blood serum. Creatinine is a waste product produced by the muscles and filtered by the kidneys.

Why might I need this test?

A urine-to-serum creatinine ratio may be used to help evaluate kidney filtration and the kidneys' handling of creatinine. It may be part of a broader assessment of kidney function or fluid balance.

How is the test performed?

Blood and urine samples are measured in the laboratory, and the urine creatinine value is compared with the serum creatinine value to calculate the ratio. Samples may need to be collected close together for the most useful comparison.

How do I prepare for the test?

Fasting is usually not required. Follow the laboratory's instructions for urine collection and timing, and tell your care team if you have a known kidney condition, are pregnant, or have recently changed medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine/Serum Creatinine Ratio

Frequently asked questions

Is this the same as an estimated glomerular filtration rate?
No. Estimated GFR estimates how well the kidneys filter blood, while this test directly compares urine and blood creatinine concentrations. Your care team may review both results together.
Can this test diagnose chronic kidney disease?
No single ratio diagnoses chronic kidney disease. Diagnosis usually requires several findings, including persistent changes in kidney function, urine albumin, or other markers over time.
What can change my result?
Dehydration, recent fluid intake, muscle mass, pregnancy, medications, and certain kidney conditions can affect the ratio. Collection timing and following the laboratory's instructions are important.
  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