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Sodium concentration in whole blood

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

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

Quick summary

["Sodium levels help doctors check for dehydration, kidney issues, or other health concerns."]

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

Key facts at a glance

LOINC
39792-7
Short code
Sodium BldC-sCnc
Synonyms
Sodium BldC-sCnc
Category
electrolyte
Sample
whole-blood
Container
Lavender-top (EDTA)
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
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to diagnose or monitor conditions like low or high sodium levels, which can affect how your body regulates fluids, blood pressure, and nerve signals. It may also be used to check for kidney problems, heart conditions, or dehydration.

What Does a Low or High Sodium Level Mean?

Extremely low sodium (hyponatremia) can cause headaches, confusion, or even seizures, while dangerously high sodium (hypernatremia) may lead to muscle spasms, rapid heartbeat, or coma. Mild fluctuations often don’t cause symptoms but can indicate underlying health issues.

How Is This Test Performed?

A small blood sample is drawn from a vein, usually in your arm. The sample is then analyzed in a lab to measure sodium concentration.

What Are Common Causes?

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.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: whole-blood

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical significance: Sodium levels are critical for maintaining fluid balance, nerve function, and blood pressure. Abnormal results may signal dehydration, kidney dysfunction, heart conditions, or hormonal imbalances, prompting further medical evaluation.

Short name

Sodium Level (Whole Blood)

Frequently asked questions

What does a normal sodium level mean for my health?
A normal sodium level (typically within a healthcare provider’s specific reference range) suggests your body is maintaining fluid and electrolyte balance well. However, even if your result is normal, other factors like diet, medications, or activity levels may still affect your sodium levels.
Can I adjust my diet to help sodium levels?
Yes, but only under guidance from your healthcare provider. Avoiding excessive salt intake or increasing fluids may help if your sodium level is low, while monitoring salt and fluid intake is important if levels are high.
Will I need to prepare for this test?
No special preparation is usually needed, but avoid excessive salt or fluid intake 24 hours before the test if instructed by your provider.
  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