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Serum/plasma sodium concentration (mass concentration)

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of sodium in your blood plasma or serum, an electrolyte critical for balancing fluids and maintaining nerve and muscle function.

Quick summary

["Sodium levels help diagnose conditions like dehydration, kidney issues, or high blood pressure."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
23914-5
Short code
OF .45% NaCl NFr RBC
Synonyms
OF .45% NaCl NFr RBC
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
4.2
Ref high
5.9
Critical range
2 N/A – 7 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85041
SNOMED
900000000000003001
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 check for imbalances that could cause symptoms like excessive thirst, confusion, muscle weakness, or irregular heartbeat. It’s often used when you have symptoms of dehydration, kidney problems, or conditions like heart failure or certain hormonal disorders.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader metabolic panel. Bring any medications you’re currently taking, as some can affect results.

How the Test Is Performed

A blood sample is drawn from a vein, usually in your arm, using a small needle. The blood is then sent to a lab for analysis. The test typically takes a few minutes, and you may feel slight discomfort but no lasting effects.

What the Results Mean

Results are compared to standard ranges for your age and health status. Low sodium (hyponatremia) or high sodium (hypernatremia) can signal underlying health concerns that need medical attention.

Reference range

Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Sodium Imbalances Can Affect Multiple Systems

Short name

Sodium Level

Frequently asked questions

What causes sodium levels to be too high or too low?
High sodium levels (hypernatremia) may result from excessive salt intake, kidney problems, or conditions like diabetes insipidus. Low sodium levels (hyponatremia) can occur from fluid overload, kidney failure, or conditions like heart failure or severe vomiting/diarrhea.
How long does it take to get results?
Results are usually available within 1–2 days, depending on your lab’s processing time. Your doctor will discuss them with you during your follow-up visit.
Can I eat or drink anything before this test?
If fasting is required, avoid food and liquids (except water) for the specified period. If no fasting is needed, you can eat and drink normally, but check with your provider for any restrictions.
  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 17, 2026. · Read our editorial policy