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Sodium and Creatinine, 24-Hour Urine

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

Measures sodium and creatinine in urine collected over 24 hours. It helps assess sodium intake and how well the kidneys excrete sodium and water.

Quick summary

["This test can help evaluate sodium balance, kidney function, and the need for sodium and fluid guidance."]

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

Key facts at a glance

LOINC
13809-9
Short code
Sodium/Creat 24h Ur
Synonyms
Sodium/Creat 24h Ur
Category
kidney
Sample
urine
Container
Sterile urine container
Units
N/A
Ref low
136
Ref high
145
Critical range
120 N/A – 160 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84295
SNOMED
110741000
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 sodium and creatinine in all urine collected over a full 24-hour period. Sodium reflects how much sodium is being excreted, while creatinine is used to help evaluate kidney function and account for urine concentration.

Why might I need this test?

A clinician may order this test to assess sodium balance, investigate unusual fluid retention or salt loss, or monitor kidney function and treatment. It may also help guide sodium and fluid recommendations for people with kidney, heart, or blood-pressure conditions.

How is the test performed?

You collect all urine for exactly 24 hours into a special container provided by the laboratory. The urine is then sent to the laboratory, where sodium and creatinine are measured and the total daily amounts are calculated.

How do I prepare for the test?

Follow the collection instructions provided by your healthcare professional, including the start and end times. Tell the laboratory and clinician about medicines, supplements, and major changes in salt or fluid intake, and ask how to handle the collection if you miss a sample.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: urine

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings2

Short name

24-Hour Urine Sodium and Creatinine

Frequently asked questions

Do I need to change my diet before this test?
Do not deliberately change your salt intake unless your clinician tells you to. Keep your usual diet and fluid habits as consistent as possible, and ask for instructions if you are taking diuretics or other medicines.
What if I miss part of the 24-hour urine collection?
Tell the laboratory or clinician, because an incomplete collection can make the results unreliable. Depending on the instructions, you may need to restart the collection.
Why are both sodium and creatinine measured?
Sodium shows how much salt is being lost in the urine, while creatinine provides information about kidney function and helps interpret the urine measurements. Together, they give a more useful picture of sodium and fluid balance.
  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