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Serum/plasma concentration of sodium (Na⁺) measured by ion-selective electrode

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 the right balance of water in your body.

Quick summary

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

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

Key facts at a glance

LOINC
14846-0
Short code
NAPA SerPl-sCnc
Synonyms
NAPA SerPl-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Is This Test Done?

Your doctor may order this test to diagnose or monitor conditions like high blood pressure, dehydration, kidney problems, or certain heart or lung diseases. It can also help check for conditions like hyponatremia (low sodium) or hypernatremia (high sodium).

What Does a Low or High Sodium Level Mean?

Low sodium levels (hyponatremia) can cause headaches, confusion, nausea, or even seizures in severe cases. High sodium levels (hypernatremia) may lead to thirst, dry mouth, or irregular heartbeat. Your doctor will interpret results based on your symptoms and overall health.

How Is This Test Performed?

A small blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where sodium levels are measured using an ion-selective electrode, which detects sodium ions in the serum or plasma.

What Are Common Causes?

Common causes of low sodium include excessive sweating, vomiting, diarrhea, or certain medications. High sodium levels may result from dehydration, kidney problems, or overuse of salt.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium Level (Serum/Plasma)

Frequently asked questions

What happens if my sodium level is out of range?
If your sodium level is too low or too high, your doctor may recommend changes in your diet, medications, or fluid intake to bring it back to a healthy range. Severe imbalances may require medical treatment, such as intravenous fluids.
How often should I get this test?
Your doctor will determine how often you need this test based on your health condition and symptoms. Some people may need it monthly or more frequently if they have ongoing health issues.
Can I eat or drink anything before the test?
You may eat and drink normally before the test unless your doctor instructs otherwise. Avoiding certain foods or fluids for a few hours before the test can sometimes affect results, so follow your doctor’s specific instructions.
  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