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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 electrolyte, in your blood. Sodium helps regulate fluid balance and nerve function.

Quick summary

["Sodium levels help doctors check if you have too much or too little fluid in your body."]

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

Key facts at a glance

LOINC
14055-8
Short code
Sodium Stl-sCnt
Synonyms
Sodium Stl-sCnt
Category
electrolyte
Sample
stool
Container
Clean container
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 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to diagnose or monitor conditions like dehydration, kidney problems, heart disease, or high blood pressure. It can also help check for electrolyte imbalances that may cause weakness, confusion, or irregular heartbeat.

What Does a Low or High Sodium Level Mean?

Low sodium (hyponatremia) can cause headaches, nausea, confusion, or seizures. High sodium (hypernatremia) may lead to thirst, dry mouth, or swelling in the brain if severe. Your doctor will interpret results based on your symptoms and overall health.

How Is This Test Performed?

A blood sample is taken from a vein in your arm. The sample is sent to a lab where it is analyzed to measure sodium levels using an automated method that detects the mineral’s presence in your blood.

What Are Common Causes?

Causes of low sodium include excessive sweating, vomiting, diarrhea, or certain medications. High sodium levels can result from dehydration, kidney issues, or overuse of salt or diuretics.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: stool

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Sodium

Frequently asked questions

What happens if my sodium level is out of range?
If your sodium level is too low or too high, your doctor may recommend changes to your diet, medications, or fluid intake. Severe imbalances may require medical treatment, such as intravenous fluids or special medications.
How often should I get 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 may only need it once a year or less.
Does diet affect sodium test results?
Yes, eating too much salt or drinking too much water can temporarily change your sodium levels. Your doctor may ask you to avoid extreme changes in diet or fluid intake before the test.
  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