Serum or Plasma Sodium (Mass Concentration)
This test measures the amount of sodium, a key mineral, in your blood. Sodium helps balance fluids and maintain proper heart and muscle function.
["Sodium levels help doctors check for dehydration, kidney issues, or other health concerns."]
Key facts at a glance
- LOINC
- 23919-4
- Short code
- OF .65% NaCl NFr RBC
- Synonyms
- OF .65% 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, high blood pressure, kidney disease, or electrolyte imbalances. It’s also used to check for conditions such as heart problems or certain types of seizures.
What to Expect Before the Test
No special preparation is needed. You may drink water before the test, but avoid eating or smoking for a short time afterward. If you’re on a low-sodium diet, follow your doctor’s instructions carefully.
What Happens During the Test?
A small needle will be inserted into your arm or hand to draw a blood sample. The process is quick and usually painless. If you’re nervous, let your healthcare provider know so they can help make it more comfortable.
What to Expect After the Test
You may feel a slight bruise or soreness at the injection site, which should go away in a few days. Apply a cold compress if needed. Avoid heavy lifting or strenuous activity for a short time to prevent excessive bleeding.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low sodium levels (hyponatremia) can cause headaches, confusion, nausea, or even seizures in severe cases. High sodium levels (hypernatremia) may lead to thirst, fatigue, or irregular heartbeat. Both extremes can signal underlying health issues that need medical attention.
Short name
Sodium
Frequently asked questions
How long does it take to get my results?
Can I eat or drink anything before the test?
What if my sodium level is outside the normal range?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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