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

Quick summary

["Sodium levels help doctors check if you’re dehydrated, have kidney issues, or need electrolyte adjustments."]

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

Key facts at a glance

LOINC
30558-1
Short code
Sodium TPN-sCnc
Synonyms
Sodium TPN-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?

Doctors order sodium tests to diagnose conditions like dehydration, high blood pressure (hypertension), or kidney problems. It may also be checked if you’re taking certain medications that affect sodium levels or if you have symptoms like excessive thirst, swelling, or confusion.

What to Expect Before the Test

No special preparation is needed. A simple blood draw is all that’s required. If you’re on a low-sodium diet or taking medications like diuretics, your doctor may advise adjustments beforehand.

What the Results Mean

Results are compared to a standard range for healthy adults. Low sodium (hyponatremia) or high sodium (hypernatremia) can signal underlying health concerns that need medical attention.

Common Causes of Abnormal Results

Low sodium can result from excessive sweating, vomiting, diarrhea, or certain medications. High sodium may occur from dehydration, kidney problems, or overuse of salt.

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.

Sodium levels are critical for maintaining fluid balance, nerve function, and blood pressure. Abnormal levels can lead to serious complications like seizures, confusion, or heart problems, so results should always be reviewed by a healthcare provider.

Short name

Sodium Level

Frequently asked questions

What triggers a sodium test?
A sodium test may be ordered if you have symptoms like unusual thirst, swelling, confusion, or if your doctor suspects conditions like dehydration, kidney disease, or high blood pressure.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time.
Can I eat or drink before the test?
You can eat and drink normally before the test unless your doctor specifies otherwise, as sodium is found in foods and fluids.
  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