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Sodium concentration in serum/plasma

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 for dehydration, kidney problems, or other health concerns."]

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

Key facts at a glance

LOINC
2951-2
Short code
Sodium SerPl-sCnc
Synonyms
Sodium SerPl-sCnc
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
136
Ref high
145
Critical range
120 N/A – 160 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84295
SNOMED
110741000
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 disease, or electrolyte imbalances. It’s also used to check for conditions like hyponatremia (low sodium) or hypernatremia (high sodium).

What Does the Result Mean?

Results are typically reported in milliequivalents per liter (mEq/L). Low sodium levels may indicate fluid loss or kidney issues, while high levels could suggest dehydration or overuse of certain medications.

Common Conditions Affecting Sodium Levels

Changes in sodium levels can occur due to vomiting, diarrhea, excessive sweating, kidney problems, or certain medications. Chronic conditions like heart or liver disease may also influence sodium balance.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where sodium concentration is measured using a specialized instrument.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium Level (Serum/Plasma)

Frequently asked questions

What are the normal ranges for sodium?
Normal sodium levels in blood are generally between 135 and 145 mEq/L, but this can vary slightly by lab. Your specific range will be provided with your results.
How long does it take to get the results?
Test results are usually available within 1 to 2 business days, depending on your lab’s processing time.
Can I eat or drink before this test?
For most sodium tests, you can eat and drink normally. However, if your doctor has specific instructions, follow them to ensure accurate results.
  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