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24-Hour Urinary Sodium and Chloride Concentration (Mass Concentration)

Published: August 9, 2026Updated: August 17, 2026

This test measures how much sodium and chloride (key electrolytes) are excreted in your urine over a 24-hour period. It helps assess kidney function and balance of fluids and electrolytes in your body.

Quick summary

["Helps diagnose and monitor conditions related to fluid and electrolyte balance."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
31104-3
Short code
OF .85% NaCl 24h Inc NFr RBC
Synonyms
OF .85% NaCl 24h Inc NFr RBC
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
4.2
Ref high
5.9
Critical range
2 N/A – 7 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85041
SNOMED
900000000000003001
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Matters

Your kidneys filter waste and excess electrolytes from your blood, passing them into urine. This test checks if your kidneys are working properly to remove sodium and chloride, which can help prevent conditions like high blood pressure or fluid imbalances.

What to Expect Before the Test

You’ll need to collect all urine for 24 hours, starting and ending with your first urine of the next day. Keep the sample refrigerated and bring it to the lab on time. Follow any special instructions your provider gives you, such as avoiding certain foods or medications.

How the Test Works

Your urine is analyzed to determine the total amount of sodium and chloride excreted. This helps doctors evaluate how well your body is managing fluid and electrolyte levels.

Common Conditions Monitored

This test is often used to diagnose or monitor conditions like hypertension (high blood pressure), kidney disease, or syndromes involving abnormal fluid retention or electrolyte imbalances.

Reference range

Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormally high sodium or chloride levels in urine may indicate kidney problems, excessive sweating, or certain metabolic disorders. Low levels could suggest kidney dysfunction, overhydration, or conditions like syndrome of inappropriate antidiuretic hormone (SIADH). Your healthcare provider will review your results in relation to your overall health and symptoms to guide further action.

Short name

24-Hour Urine Sodium & Chloride

Frequently asked questions

What does a high or low result mean?
A high result may signal issues like kidney disease, excessive sodium intake, or conditions that cause the body to retain fluid. A low result might suggest overhydration, kidney problems, or certain hormonal imbalances. Your doctor will discuss these findings with you based on your medical history and other test results.
How often should I get this test?
Your doctor will determine how often you need this test based on your health condition. For example, people with kidney disease or hypertension may need it more frequently to monitor their condition. Regular follow-ups are important to adjust treatments if needed.
Can diet or medications affect this test?
Yes, certain foods (like salty snacks), medications (such as diuretics), or health conditions (like kidney disease) can influence your sodium and chloride levels. Always inform your healthcare provider about any medications or dietary changes before the test.
  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 17, 2026. · Read our editorial policy