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Sodium concentration in urine (24-hour collection)

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

This test measures how much sodium your body excretes in urine over a full day. Sodium helps balance fluids and supports nerve and muscle function.

Quick summary

["Assesses kidney function and fluid balance in 24-hour urine samples."]

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

Key facts at a glance

LOINC
57382-4
Short code
Sodium 2h Ur-sCnc
Synonyms
Sodium 2h 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 Is This Test Done?

Your doctor may order this test to check if your kidneys are properly removing sodium from your body. It can also help diagnose conditions like kidney disease, high blood pressure, or certain hormonal imbalances that affect fluid and electrolyte levels.

What to Expect Before the Test

You’ll need to collect all urine for 24 hours, starting from one full wake-up time (e.g., midnight) and ending at the same time the next day. Drink plenty of fluids but avoid foods high in sodium unless instructed otherwise.

How the Test Works

After collecting urine, it’s sent to a lab where sodium levels are measured using a specialized method to ensure accurate results.

Common Conditions Monitored

High or low urine sodium levels may signal issues like kidney problems, heart failure, or certain medications affecting fluid balance.

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 findings1

Short name

24-Hour Urine Sodium

Frequently asked questions

What does a low urine sodium level mean?
A low urine sodium level may suggest your body is retaining too much sodium, possibly due to kidney issues, dehydration, or certain medications. Your doctor may investigate further to rule out conditions like kidney disease or excessive fluid loss.
What does a high urine sodium level mean?
High urine sodium levels might indicate your kidneys aren’t properly excreting sodium, which can happen with kidney problems, excessive salt intake, or conditions like primary hyperaldosteronism.
Can diet affect urine sodium levels?
Yes, diet plays a role. Eating high-sodium foods or drinking less water can raise urine sodium levels, while a low-sodium diet or increased fluid intake may lower them. Follow your doctor’s guidance on dietary adjustments.
  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