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Sodium concentration in urine (24-hour urine collection)

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

This test measures the amount of sodium (a key electrolyte) found in your urine over a full day. It helps assess how well your kidneys are balancing sodium levels in your body.

Quick summary

["Understanding your sodium balance through daily urine output is important for managing kidney function and blood pressure."]

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

Key facts at a glance

LOINC
57370-9
Short code
Sodium 12h Ur-sCnc
Synonyms
Sodium 12h 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 healthcare provider may order this test if you have symptoms like high blood pressure, swelling, kidney problems, or if you’re taking medications that affect sodium levels. It can also help diagnose conditions like syndrome of inappropriate antidiuretic hormone (SIADH) or certain kidney disorders.

What to Expect Before the Test

You’ll need to collect all urine for a full 24-hour period, typically starting after midnight on one day and ending midnight the next. Drink plenty of fluids to help your urine flow naturally. Avoid special diets unless instructed by your doctor.

How the Test Works

After collecting your urine sample, it’s sent to a lab where sodium is measured using a specialized test method. The lab will analyze the total sodium content in your urine over the 24-hour period.

What the Results Mean

Results are usually reported as the total sodium amount in grams or milligrams per day. High levels may suggest conditions like kidney disease or excessive salt intake, while low levels could indicate problems with fluid balance or certain hormonal imbalances.

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.

Clinical Significance

Short name

24-Hour Urine Sodium

Frequently asked questions

What causes high sodium levels in urine?
High sodium levels in urine can occur due to kidney issues (like nephrotic syndrome), excessive salt intake, or certain medications. It may also be linked to conditions affecting how your body regulates fluids, such as SIADH.
What causes low sodium levels in urine?
Low sodium levels in urine might indicate problems with fluid retention, kidney dysfunction, or hormonal imbalances (like low aldosterone). It can also be seen in patients with certain medications or conditions affecting kidney function.
How often should I get this test?
The frequency depends on your health condition. Your doctor may recommend this test periodically if you have ongoing kidney issues, high blood pressure, or are taking medications that affect sodium balance. Follow-up may be needed every few months or as directed by your healthcare provider.
  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