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Sodium concentration in blood (serum/plasma)

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."]

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

Key facts at a glance

LOINC
41657-8
Short code
Sodium BldMV-sCnc
Synonyms
Sodium BldMV-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 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 heart failure, kidney disease, or certain medications that affect sodium balance.

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. It usually takes a few minutes, and you may feel a brief pinch. If done at home, ensure you’re well-hydrated unless instructed otherwise.

What Happens During the Test?

Blood is collected into a tube and sent to a lab for analysis. The test measures sodium concentration in the serum or plasma portion of your blood.

Results and Follow-Up

Results are typically ready within a few days. High or low sodium levels may prompt further testing or adjustments to your treatment plan, such as fluid intake or medication.

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 outside normal ranges can cause serious health issues, like seizures (low sodium), or worsening heart/kidney problems (high sodium). Your doctor will interpret results in the context of your overall health.

Short name

Sodium Level

Frequently asked questions

What causes sodium levels to be too high or too low?
High sodium (hypernatremia) can result from dehydration, kidney problems, or excessive salt intake. Low sodium (hyponatremia) may occur from excessive fluid loss, kidney disease, or certain medications.
How long does it take to get results?
Results are usually available within 1–3 business days, depending on your lab’s processing time.
Can I eat or drink before this test?
No restrictions apply unless your doctor specifies. However, if you’re taking medications that affect sodium, check with them first.
  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