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Serum or plasma mass concentration of sodium (measured by ion-selective electrode)

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

This test measures the amount of sodium, an essential electrolyte, in your blood. Sodium helps balance fluids and maintain proper heart and nerve function.

Quick summary

["Sodium helps regulate fluid balance and nerve function; low or high levels can cause serious health issues."]

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

Key facts at a glance

LOINC
50500-8
Short code
GH sp8 SerPl-mCnc
Synonyms
GH sp8 SerPl-mCnc
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

What Is Sodium Used For in the Body?

Sodium is crucial for several bodily functions, including maintaining fluid balance, supporting nerve and muscle function, and helping regulate blood pressure. It also plays a role in the movement of nutrients and waste products across cell membranes.

Why Might Your Sodium Level Be Tested?

Your doctor may order a sodium test if you have symptoms like excessive thirst, confusion, muscle weakness, or irregular heartbeat. It’s also checked during monitoring for conditions like kidney disease, heart failure, or dehydration.

What Can Affect Your Sodium Levels?

Several factors can influence sodium levels, including diet (too much or too little salt), dehydration or overhydration, certain medications (like diuretics), kidney problems, or hormonal imbalances (such as low aldosterone).

What Are Common Symptoms of Sodium Imbalance?

Low sodium (hyponatremia) may cause headaches, nausea, fatigue, or seizures, while high sodium (hypernatremia) can lead to dry mouth, rapid heartbeat, or confusion. Symptoms depend on how quickly levels change.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium level

Frequently asked questions

How often will I need this test?
Sodium levels are often checked as part of a routine blood panel or when monitoring conditions like kidney disease, heart problems, or dehydration. Your doctor will determine how frequently this test is needed based on your health status and symptoms.
What does a low sodium level mean?
A low sodium level (hyponatremia) may indicate overhydration, kidney issues, or conditions like heart or liver disease. It can also be caused by excessive sweating, vomiting, or certain medications. Your doctor will discuss treatment options, such as adjusting fluids or medications.
What does a high sodium level mean?
A high sodium level (hypernatremia) may suggest dehydration, excessive salt intake, or conditions like kidney problems or adrenal insufficiency. Treatment often involves managing fluids, reducing salt intake, or addressing underlying causes like hormonal imbalances.
  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