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Creatinine, Urine and Serum

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

Measures creatinine in urine and blood serum. Comparing the two results can help evaluate kidney function and how the kidneys handle creatinine.

Quick summary

["Urine and serum creatinine results are interpreted together to help assess kidney function and hydration."]

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

Key facts at a glance

LOINC
81796-5
Short code
THB/Creat Ur-sRto
Synonyms
THB/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?

Creatinine is a waste product made by the muscles and removed from the body by the kidneys. This test measures creatinine in urine and in blood serum.

Why might I need this test?

Creatinine in serum helps assess kidney filtering ability, while a urine measurement can show how much creatinine is being excreted. The results may be used together to evaluate kidney function, hydration, or the effect of medicines.

How is the test performed?

A blood sample is drawn from a vein to measure serum creatinine. A urine sample is collected and tested separately, following the collection instructions provided by the laboratory.

How do I prepare for the test?

Fasting is usually not required, but follow any instructions from your clinician or laboratory. Drink fluids normally unless you have been given other guidance, and be sure to collect the urine sample using the container and timing specified.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

High serum creatinine may indicate reduced kidney filtering ability, although dehydration and certain medicines can also affect the result. Urinary creatinine varies with urine concentration and muscle mass, so urine and serum results are best interpreted together with the rest of the clinical evaluation.

Short name

Urine and Serum Creatinine

Frequently asked questions

Is fasting required for this test?
Fasting is usually not necessary. Follow any specific preparation instructions provided by your healthcare professional.
Why are urine and blood creatinine tested together?
Serum creatinine reflects creatinine in the blood, while urine creatinine reflects how much is being released in the urine. Comparing them can provide additional information about kidney function.
Does a high creatinine level always mean kidney disease?
No. Dehydration, muscle mass, medicines, and other conditions can influence creatinine levels, so results should be reviewed with your clinician.
  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