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Serum or plasma concentration of sodium (electrolyte)

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

This test measures the amount of sodium in your blood, an important electrolyte that helps balance fluids and support nerve and muscle function.

Quick summary

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

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

Key facts at a glance

LOINC
32932-6
Short code
SN-FH Angle Skull CT
Synonyms
SN-FH Angle Skull CT
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct-measured
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 if you have symptoms like excessive thirst, confusion, swelling, or irregular heartbeat. It’s also used to monitor conditions like heart failure, kidney disease, or hormonal imbalances.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw blood. If you’re on a low-sodium diet, check with your doctor first.

What the Results Mean

Results are compared to a general reference range (typically 135–145 mEq/L in serum/plasma), but your doctor will interpret them based on your health and symptoms.

Common Conditions Affecting Sodium Levels

Low sodium (hyponatremia) can cause headaches, nausea, or seizures, while high sodium (hypernatremia) may lead to dry mouth, rapid heartbeat, or muscle cramps. Both can stem from fluid loss, kidney problems, or excessive salt intake.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium Level

Frequently asked questions

What causes low sodium levels in the blood?
Low sodium can result from excessive water intake, kidney problems, vomiting, diarrhea, or certain medications (e.g., diuretics). Symptoms may include confusion or fatigue.
What causes high sodium levels in the blood?
High sodium levels often occur due to dehydration, kidney disease, excessive salt intake, or conditions like diabetes insipidus. Symptoms may include thirst, dry mouth, or muscle weakness.
How often should I get this test?
Your doctor will determine frequency based on your health needs—this may be routine (e.g., every few months) or triggered by symptoms or ongoing conditions.
  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