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Sodium concentration in plasma (serum/plasma)

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

This test measures the amount of sodium, a key electrolyte, in your blood plasma. Sodium helps balance fluids and maintain normal heart rhythm.

Quick summary

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

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

Key facts at a glance

LOINC
75681-7
Short code
Deprecated P aeruginosa sodA Bld Pos Ql Prb Mag
Synonyms
Deprecated P aeruginosa sodA Bld Pos Ql Prb Mag
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-mag-capture
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 doctor may order this test to diagnose or monitor conditions like dehydration, high blood pressure, kidney disease, or electrolyte imbalances. It’s also used to check for conditions like congestive heart failure or certain types of kidney stones.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw a blood sample. If you’re on a sodium-restricted diet, let your doctor know.

What the Results Mean

Results are compared to a standard range for healthy adults, but exact values can vary by lab. Low sodium (hyponatremia) may cause headaches or confusion, while high sodium (hypernatremia) could lead to muscle spasms or rapid heartbeat.

Common Conditions Affecting Sodium Levels

Abnormal sodium levels can result from conditions like excessive sweating, vomiting, diarrhea, kidney problems, or certain medications. Chronic conditions like heart or liver disease may also play a role.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Sodium levels are critical for overall bodily function, including nerve and muscle activity. Chronic imbalances can lead to serious complications like seizures, coma, or heart failure. Your doctor will interpret results in the context of your medical history and symptoms.

Short name

Serum/plasma sodium

Frequently asked questions

What causes low sodium levels?
Low sodium levels (hyponatremia) can occur due to excessive water intake, kidney problems, heart or liver disease, certain medications (like diuretics), or conditions causing excessive vomiting or diarrhea.
What causes high sodium levels?
High sodium levels (hypernatremia) may result from dehydration, kidney disease, excessive salt intake, diabetes insipidus, or conditions that cause excessive loss of fluids (e.g., sweating, burns).
Can sodium levels change quickly?
Yes, sodium levels can fluctuate rapidly depending on fluid balance, diet, and health conditions. If you notice symptoms like confusion, muscle weakness, or irregular heartbeat, seek medical attention immediately.
  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