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Serum or plasma concentration of sodium (electrolyte measurement)

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

This test measures the amount of sodium, a key mineral, in your blood. Sodium helps balance fluids and maintain normal blood pressure and the function of nerves and muscles.

Quick summary

["Sodium levels help doctors check if you have too much or too little sodium, which can affect your health."]

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

Key facts at a glance

LOINC
32925-0
Short code
SNB Angle Skull XR
Synonyms
SNB Angle Skull XR
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr-measured
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

What Is Sodium’s Role in the Body?

Sodium is essential for regulating blood pressure, balancing fluids in your body, and transmitting nerve signals. It also helps maintain the proper function of muscles and cells. Too much or too little sodium can lead to health issues like high blood pressure, dehydration, or swelling.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms like excessive thirst, confusion, swelling in the legs or ankles, muscle cramps, or irregular heartbeat. It’s also used to monitor conditions like kidney disease, heart problems, or certain medications that affect sodium levels.

Common Causes of Abnormal Results

High sodium levels (hypernatremia) can occur from dehydration, excessive salt intake, or certain medical conditions like kidney problems or diabetes. Low sodium levels (hyponatremia) may result from vomiting, diarrhea, excessive sweating, or conditions like heart or kidney failure.

How Is This Test Performed?

A small blood sample is taken from a vein in your arm. The sample is sent to a lab, where it’s analyzed to measure sodium concentration using a specialized test method. The results help your doctor assess your electrolyte balance.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Sodium Levels and Health Risks

Short name

Sodium Level

Frequently asked questions

How often do I need this test?
The frequency depends on your health condition and treatment. Some people need this test regularly, while others may only need it once if they have a specific issue like kidney disease or high blood pressure.
What do my sodium test results mean?
Results are usually compared to a standard range, but your doctor will explain what your specific numbers mean in the context of your health. Very high or very low sodium levels can signal serious problems that need medical attention.
Can I eat or drink anything before the test?
Generally, you can eat and drink normally unless your doctor instructs otherwise. Some tests may require fasting, but sodium tests usually don’t have strict dietary restrictions before collection.
  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