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Serum or plasma mass concentration of sodium

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

This test measures the amount of sodium in your blood, which helps regulate fluid balance, nerve and muscle function, and blood pressure.

Quick summary

["Sodium levels help doctors assess hydration, kidney function, and potential electrolyte imbalances."]

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

Key facts at a glance

LOINC
3834-9
Short code
NAPA SerPl-mCnc
Synonyms
NAPA 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

Why Is This Test Done?

Your doctor may order this test to check for conditions like dehydration, overhydration, kidney disease, or hormonal imbalances that affect sodium levels. It’s also used in monitoring treatments for conditions such as heart failure or certain types of kidney disorders.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw if your doctor specifies. Wear a loose shirt for easy access to your arm.

How the Test Works

A small amount of blood is drawn from a vein in your arm. The sample is then sent to a lab where it is analyzed to determine the sodium concentration in your blood.

Possible Results and Their Meaning

High sodium levels (hypernatremia) may indicate dehydration, excessive salt intake, or certain medical conditions. Low sodium levels (hyponatremia) could signal overhydration, kidney problems, or adrenal insufficiency. Your doctor will interpret results in relation to your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium Level

Frequently asked questions

What causes sodium levels to be too high?
High sodium levels may be caused by dehydration, excessive salt intake, kidney disease, or certain hormonal imbalances, such as hyperaldosteronism. Rarely, it can also occur due to overuse of certain medications or conditions like Cushing’s syndrome.
What causes sodium levels to be too low?
Low sodium levels (hyponatremia) are often linked to overhydration, kidney or liver disease, heart failure, vomiting or diarrhea, or certain medications like diuretics or antidepressants. It can also occur in conditions where the body retains too much water, such as syndrome of inappropriate antidiuretic hormone (SIADH).
How often should I get this test?
Your doctor will determine how often you need this test based on your health condition, symptoms, and treatment plan. Regular monitoring may be necessary if you have chronic illnesses like kidney disease, heart failure, or if you take medications that affect sodium levels.
  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