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Serum or plasma concentration of sodium (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 normal blood pressure.

Quick summary

["Sodium levels help doctors check if your body is retaining or losing too much fluid or salt."]

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

Key facts at a glance

LOINC
51856-3
Short code
S aureus TSST-1 IgE Qn
Synonyms
S aureus TSST-1 IgE Qn
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 This Test Might Be Ordered

Your doctor may order this test if you have symptoms like excessive thirst, swelling, confusion, or irregular heartbeat. It’s also used to monitor conditions like heart failure, kidney disease, or high blood pressure.

What to Expect Before the Test

No special preparation is needed, but you may need to fast for 8–12 hours if your blood is drawn early in the morning. Avoid excessive salt intake 24 hours before testing.

How the Test Is Performed

A healthcare provider will take a blood sample from a vein in your arm using a small needle. You may feel a brief pinch, but it usually doesn’t cause pain. The sample is sent to a lab for analysis.

What the Results Mean

Results are compared to a standard range, but exact values can vary by lab. Low sodium (hyponatremia) may cause headaches or muscle cramps, while high sodium (hypernatremia) could lead to dehydration symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium level

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–2 business days, depending on your lab’s processing time.
Can I eat or drink anything before the test?
If fasting is required, avoid food and liquids (except water) for 8–12 hours before your blood draw. Check with your doctor for specific instructions.
What if my sodium level is outside the normal range?
If your results are abnormal, your doctor will discuss possible causes and next steps, such as further testing or changes to your treatment plan.
  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