Sodium concentration in serum/plasma (24-hour urine collection)
This test measures how much sodium your body excretes in urine over 24 hours. Sodium helps balance fluids and maintain normal blood pressure.
["Assesses kidney function and fluid balance by tracking sodium loss in urine over a full day."]
Key facts at a glance
- LOINC
- 74685-9
- Short code
- Sodium 4h Ur-sCnc
- Synonyms
- Sodium 4h Ur-sCnc
- Category
- electrolyte
- 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
Why This Test Is Done
Your doctor may order this test if you have symptoms like high blood pressure, swelling, or signs of fluid imbalance. It can also help diagnose conditions like kidney disease, syndrome of inappropriate antidiuretic hormone (SIADH), or certain electrolyte disorders.
What to Expect Before the Test
You’ll need to collect all urine for 24 hours, starting after midnight of the day the test begins. Store the urine in a refrigerator and return it to the lab the same day. Follow your doctor’s instructions carefully to ensure accurate results.
What Happens During the Test
No special preparation is needed beyond the urine collection. The lab analyzes the urine sample for sodium concentration, which is compared to your body’s typical sodium balance.
Results and Interpretation
Results help determine if your kidneys are properly filtering sodium or if fluid retention is occurring. Abnormal results may signal conditions requiring medical attention, such as kidney dysfunction or hormonal imbalances.
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.
Clinical Significance: Sodium balance is critical for nerve function, muscle contractions, and blood pressure regulation. Abnormally high or low sodium levels can cause serious health issues, including seizures, confusion, or kidney damage. This test helps identify whether sodium loss or retention is affecting your health.
Short name
24-Hour Sodium Urine Test
Frequently asked questions
What causes a doctor to request this test?
How long does it take to get results?
Can I drink water during the 24-hour urine collection?
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