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Serum/plasma sodium concentration (mass concentration)

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

This test measures the amount of sodium in your blood plasma or serum, which helps assess your body’s balance of fluids and electrolytes.

Quick summary

["Sodium levels help determine if you’re retaining or losing too much fluid or salt."]

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

Key facts at a glance

LOINC
23915-2
Short code
OF .50% NaCl NFr RBC
Synonyms
OF .50% NaCl 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 Sodium Levels Matter

Sodium is a key electrolyte that helps regulate blood pressure, fluid balance, and nerve function. Abnormal levels can cause symptoms like confusion, muscle cramps, or irregular heartbeat.

How the Test Works

A small blood sample is drawn and analyzed to measure sodium concentration using a specialized lab technique. Results are compared to standard reference ranges for your age and health status.

What to Expect Before the Test

No special preparation is needed, but avoid eating or drinking anything (except water) for 4–6 hours before the test if instructed by your provider.

Possible Causes of Abnormal Results

High sodium levels (hypernatremia) may occur from dehydration, excessive salt intake, or kidney problems. Low sodium levels (hyponatremia) can result from excessive sweating, vomiting, or certain medications.

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.

Clinical Significance

Short name

Sodium Level

Frequently asked questions

What does a sodium test tell your doctor?
Your doctor may order this test to diagnose conditions like dehydration, heart or kidney disease, or hormonal imbalances. Repeated tests help track fluid and electrolyte changes over time.
How long does it take to get results?
Results are typically available within 1–2 business days, depending on your lab. Follow-up with your provider to discuss findings and next steps.
Can I eat or drink before this test?
Most sodium tests require fasting for 4–6 hours before drawing blood, but always confirm with your healthcare provider for your specific 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