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Sodium in Blood (Serum/Plasma) Concentration

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

This test measures the amount of sodium, a key mineral, in your blood. Sodium helps balance fluids and maintain normal blood pressure and nerve/muscle function.

Quick summary

["Sodium levels help doctors check for dehydration, kidney issues, or conditions like high blood pressure or heart problems."]

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

Key facts at a glance

LOINC
32717-1
Short code
Sodium BldA-sCnc
Synonyms
Sodium BldA-sCnc
Category
electrolyte
Sample
whole-blood
Container
Lavender-top (EDTA)
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
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why It’s Done

Your doctor may order this test if you have symptoms like extreme thirst, confusion, swelling, or irregular heartbeat. It’s also used to monitor conditions like heart failure, kidney disease, or electrolyte imbalances.

What to Expect

A small blood sample is taken from your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The test is quick and requires no special preparation.

Normal vs. Abnormal Results

While reference ranges vary by lab, sodium levels outside the typical range can signal serious health concerns. Low sodium (hyponatremia) may cause headaches or seizures, while high sodium (hypernatremia) could lead to confusion or muscle spasms.

Common Conditions Affecting Sodium

Conditions like kidney disease, heart failure, or excessive sweating can alter sodium levels. Certain medications (e.g., diuretics) or illnesses (e.g., vomiting/diarrhea) may also impact it.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: whole-blood

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Sodium levels are critical for fluid balance, nerve function, and blood pressure regulation. Abnormal results may indicate dehydration, kidney dysfunction, or metabolic disorders requiring medical attention.

Short name

Serum Sodium

Frequently asked questions

What causes sodium levels to be too low or too high?
Low sodium (hyponatremia) can result from excessive water intake, kidney problems, or certain medications. High sodium (hypernatremia) may occur from dehydration, excessive salt intake, or hormonal imbalances like diabetes insipidus.
How long does it take to get results?
Results are typically available within 1–2 business days, depending on your lab. Your doctor will discuss them with you during your follow-up visit.
Can I eat or drink anything before the test?
No special preparation is needed, but avoid excessive salt or fluids 24 hours before if instructed by your doctor.
  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