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Serum or Plasma Sodium (Electrolyte Measurement)

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

This test measures the amount of sodium in your blood, which helps your body maintain proper fluid balance, nerve function, and muscle contractions.

Quick summary

["Sodium levels help doctors check for dehydration, kidney problems, or conditions affecting fluid balance."]

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

Key facts at a glance

LOINC
10100-6
Short code
ST Slope L-V1
Synonyms
ST Slope L-V1
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
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 kidney disease, heart failure, or high blood pressure.

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 sodium-restricted diet, let your doctor know before testing.

What the Results Mean

Results are compared to a standard range for healthy adults. Too high or too low levels can signal health issues that need medical attention.

Common Conditions Affecting Sodium Levels

High sodium (hypernatremia) may occur from dehydration, kidney problems, or excessive salt intake. Low sodium (hyponatremia) can result from kidney failure, vomiting, or overuse of diuretics.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium Level

Frequently asked questions

How often will I need this test?
Your doctor will determine how often you need this test based on your health condition. Some people may need it monthly, while others only occasionally.
What are the normal ranges for sodium?
Normal sodium levels in blood typically fall between 135 and 145 milliequivalents per liter (mEq/L). Your specific range may vary slightly depending on your lab and health status.
Can diet affect sodium test results?
Yes, eating too much salt or drinking too little water can influence sodium levels. If you’re on a special diet, always inform your healthcare provider before testing.
  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