24-Hour Urine Sodium
This test measures the total amount of sodium excreted in urine over 24 hours. It can help assess sodium intake, kidney sodium handling, blood pressure, and fluid balance.
["The result estimates how much sodium your body is losing in urine and should be interpreted with hydration status, medications, and other clinical findings."]
Key facts at a glance
- LOINC
- 27257-5
- Short code
- Sodium 24h Stl-sCnt
- Synonyms
- Sodium 24h Stl-sCnt
- Category
- electrolyte
- Sample
- stool
- Container
- Clean 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
- 5 g
- Stability
- Refrigerated: 24h, Frozen: 7d
- TAT
- 4–24 hours
- Order
- routine
What the Test Measures
Urine sodium reflects sodium filtered by the kidneys and then either excreted or reabsorbed. A 24-hour collection includes all urine produced during the collection period, giving a more complete picture than a single urine sample.
How the Test Is Collected
Urine is collected for 24 hours in a labeled container provided by the laboratory. The collection begins and ends at specified times, and all urine produced during that period must be included. Ask the laboratory for exact instructions and storage requirements.
Why It May Be Ordered
Clinicians may use this test when evaluating high blood pressure, swelling, kidney function, or unusual sodium loss. It can also help estimate sodium intake when dietary assessment is uncertain and monitor selected treatments.
Factors That Can Affect the Result
Changes in fluid intake, exercise, kidney function, and medicines such as diuretics can alter urine sodium. Incomplete collections, very high or low urine volume, and deviations from the prescribed collection time may make the result less reliable.
Reference range
Adult: 136-145 mmol/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A high or low 24-hour urine sodium value can indicate increased sodium loss, reduced excretion, or changes in overall sodium balance, but it does not identify a specific cause by itself. The result is most useful when interpreted alongside blood pressure, kidney function tests, hydration status, medications, dietary sodium intake, and symptoms such as swelling or dizziness.
Short name
24-Hour Urine Sodium
Frequently asked questions
How do I prepare for a 24-hour urine sodium test?
What happens if the collection is incomplete or the urine volume is unusual?
Does a high urine sodium level always mean too much salt is being eaten?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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