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Sodium concentration in fluid (e.g., serum or plasma)

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

This test measures the amount of sodium, a key mineral, in your blood or body fluid. Sodium helps balance fluids and support nerve and muscle function.

Quick summary

["Sodium levels help doctors check if you have too much or too little sodium, which can affect your health."]

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

Key facts at a glance

LOINC
2950-4
Short code
Sodium Fld-sCnc
Synonyms
Sodium Fld-sCnc
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
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 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 to diagnose or monitor conditions like dehydration, heart disease, kidney problems, or high blood pressure. It can also help identify signs of electrolyte imbalances or certain medical emergencies.

What to Expect Before the Test

You may have this test by drawing blood from a vein in your arm. If you’re concerned about needles, let your healthcare provider know. No special preparation is usually needed, but check with them first.

What the Results Mean

Results are compared to standard ranges for sodium concentration, but exact values can vary by lab. High or low sodium levels may signal underlying health issues that need attention.

Common Conditions Affecting Sodium Levels

High sodium levels (hypernatremia) can occur from dehydration, excessive salt intake, or kidney problems. Low sodium levels (hyponatremia) may result from fluid overload, kidney disease, or certain medications.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium Level

Frequently asked questions

What causes sodium levels to change?
Sodium levels can be affected by dehydration, diet (especially high-salt foods), kidney function, heart problems, or certain medications. Illnesses like vomiting, diarrhea, or fever can also shift sodium levels quickly.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab. Your doctor will discuss them with you during your follow-up visit.
Can I eat or drink before this test?
No special diet is needed, but avoid excessive salt or fluids right before testing if instructed. Always follow your doctor’s specific instructions.
  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