Skip to content

Sodium concentration in 24-hour urine

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 blood pressure, and this test helps doctors assess kidney function and fluid balance.

Quick summary

["Helps evaluate kidney function and fluid balance in your body."]

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

Key facts at a glance

LOINC
26763-3
Short code
Sodium 2h Ur-mRate
Synonyms
Sodium 2h Ur-mRate
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?

Doctors may order a 24-hour urine sodium test to check if your kidneys are removing enough sodium, which can affect blood pressure and fluid balance. It’s also used to diagnose conditions like kidney disease, heart failure, or certain hormonal imbalances.

What to Expect Before the Test

You’ll need to collect all urine for 24 hours, starting and ending with your first morning urine. Store the sample in a refrigerator and bring it to the lab on time. Follow any special instructions your doctor provides, such as avoiding certain foods or medications.

How the Test Works

Your urine is collected in a container over 24 hours. The lab tests the sodium content in the sample to determine how much your body is excreting. This helps assess kidney function and fluid balance.

What the Results Mean

Results are typically reported as the total sodium amount excreted in milligrams (mg) over 24 hours. High or low levels may indicate underlying health issues that need further evaluation.

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 causes a high sodium urine result?
High sodium 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 fluid balance, such as heart or liver disease.
What causes a low sodium urine result?
Low sodium in urine may happen if your kidneys aren’t working well, or if you’re retaining too much fluid (e.g., from heart failure). It can also be caused by certain medications or hormonal imbalances.
How often should I get this test?
Your doctor will determine how often this test is needed based on your health condition. It may be done once or repeated if monitoring a specific issue like kidney disease or fluid balance problems.
  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