Skip to content

Serum Sodium Concentration (Substance Concentration)

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

This test measures the amount of sodium in your blood serum. Sodium is an important electrolyte that helps regulate fluid balance, nerve and muscle function, and blood pressure.

Quick summary

["Check your sodium levels to ensure your body’s fluid and electrolyte balance is healthy."]

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

Key facts at a glance

LOINC
97781-9
Short code
Sodium 4h spec Dial fld-sCnc
Synonyms
Sodium 4h spec Dial 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 healthcare provider may order this test if you have symptoms like excessive thirst, confusion, muscle cramps, or swelling, or if you have conditions such as heart disease, kidney problems, or high blood pressure. It can also be part of routine check-ups or monitoring for certain medical treatments.

What to Expect Before the Test

No special preparation is usually needed. 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 taking to your appointment.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. The blood sample is sent to a lab for analysis. The test typically takes a few minutes, and you may feel a slight pinch or discomfort during the draw.

What Do the Results Mean?

Results are compared to standard reference ranges, but exact values can vary by lab. Low sodium (hyponatremia) may cause dizziness or seizures, while high sodium (hypernatremia) could lead to dehydration or confusion. Your provider will discuss your results in the context of your health.

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 Abnormal Sodium Levels?
Sodium levels can drop due to excessive sweating, vomiting, diarrhea, kidney issues, or certain medications (like diuretics). High sodium may result from dehydration, excessive salt intake, or conditions like diabetes insipidus. Chronic imbalances can affect heart, brain, and muscle function.
How Are Sodium Levels Treated?
Treatment depends on whether sodium is too high or too low. For hyponatremia, fluids or medications may be adjusted, while hypernatremia might involve reducing salt intake or using IV fluids. Your provider will tailor treatment to your specific needs.
Can I Prevent Sodium Imbalance?
Yes! Monitor your fluid intake, limit processed foods high in salt, and stay hydrated. If you have kidney disease or other conditions, follow your provider’s advice on diet and lifestyle to help maintain balanced sodium levels.
  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