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Urea Nitrogen and Creatinine, Fluid

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

Measures urea nitrogen and creatinine in a fluid specimen to help assess kidney function, hydration, and nitrogen waste removal.

Quick summary

["This test helps evaluate kidney function and how well the body is removing metabolic waste."]

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

Key facts at a glance

LOINC
44735-9
Short code
Urea nit/Creat Fld
Synonyms
Urea nit/Creat Fld
Category
kidney
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
7
Ref high
20
Critical range
— – 100 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84520
SNOMED
2739004
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

What is this test?

Urea nitrogen and creatinine are waste products made by the body. Measuring them together helps clinicians evaluate kidney filtering and the body's handling of fluids. The specimen type should be confirmed on your test order, because results can differ between urine and blood-based samples.

Why might I need this test?

This test may be ordered to assess kidney function, investigate changes in urination, evaluate dehydration, or monitor an illness or treatment that could affect the kidneys. It may also be used alongside other laboratory tests to interpret overall health.

How is the test performed?

A laboratory analyzes the specified fluid specimen for urea nitrogen and creatinine. Depending on the test, the results may be reported as concentrations or compared with creatinine to help account for differences in urine concentration.

How do I prepare for the test?

Follow the instructions provided with your test order. If a urine specimen is required, you may be asked to provide a clean-catch or timed urine sample. Fluid intake and collection time can affect some results, so ask your healthcare professional whether any special preparation is needed.

Reference range

Adult: 7-20 mg/dLN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urea Nitrogen and Creatinine

Frequently asked questions

What does this test measure?
It measures two waste products: urea nitrogen, which reflects nitrogen handling, and creatinine, which is commonly used to assess kidney filtering.
Does the test require a urine sample?
The laboratory order identifies the required specimen. This test can use different fluids, so confirm whether a urine, serum, or another specimen is needed before collection.
What can cause abnormal results?
Abnormal results may reflect dehydration, kidney disease, medication effects, liver disease, changes in protein intake, or other health conditions. A clinician should interpret the results in your overall clinical context.
  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