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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, which helps regulate fluid balance, blood pressure, and nerve function.

Quick summary

["Sodium levels help doctors check if you’re retaining or losing too much fluid or salt."]

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

Key facts at a glance

LOINC
23912-9
Short code
OF .35% NaCl NFr RBC
Synonyms
OF .35% 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 diagnose or monitor conditions like dehydration, heart failure, kidney disease, or high blood pressure. It can also help identify electrolyte imbalances or reactions to certain medications.

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. If you’re tested at home (e.g., for 24-hour urine), follow your doctor’s instructions for collecting the sample.

What the Results Mean

Results are compared to a standard range for healthy adults, but exact values can vary by lab. Low sodium (hyponatremia) may cause headaches or confusion, while very high sodium (hypernatremia) could lead to muscle spasms or seizures.

Common Conditions Affecting Sodium Levels

Conditions like excessive sweating, vomiting, or diarrhea can lower sodium. Conversely, kidney problems, excessive salt intake, or certain medications (e.g., diuretics) may raise it. Chronic conditions like heart or liver disease can also influence levels.

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

Short name

Sodium level

Frequently asked questions

Could my sodium level be affected by my diet?
Yes, diet plays a role. High-sodium foods (like processed snacks or salty meats) can raise sodium levels, while foods like fruits or vegetables may lower it. Your doctor may recommend dietary adjustments if your levels are out of balance.
What if my sodium level is too low or too high?
If your sodium level is abnormal, your doctor may recommend treatments like fluid restriction, medications, or IV fluids to restore balance. Severe imbalances require immediate medical attention.
Why might my doctor order this test repeatedly?
If you have ongoing health issues (e.g., kidney disease, heart failure), your doctor may monitor sodium levels regularly to adjust treatments and prevent complications.
  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