Serum Sodium (Electrolyte)
This test measures the amount of sodium in your blood, an important electrolyte that helps balance fluids and maintain proper heart and nerve function.
["Sodium levels help doctors check if you're retaining or losing too much fluid or salt, which can affect your health."]
Key facts at a glance
- LOINC
- 30543-3
- Short code
- OF .75% NaCl NFr RBC
- Synonyms
- OF .75% 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 This Test Matters
Your body needs sodium to keep fluids balanced and support nerve and muscle function. Too much or too little can lead to serious health issues, like high blood pressure, heart problems, or even seizures in extreme cases. Doctors may order this test if you have symptoms like extreme thirst, confusion, or swelling, or if you’re taking certain medications that affect sodium levels.
When You Might Need It
This test is often done if you have symptoms like unusual thirst, swelling in your legs or abdomen, confusion, or irregular heartbeat. It may also be checked before surgeries, during pregnancy, or if you have conditions like kidney disease, heart failure, or certain medications (like diuretics or steroids) that can affect sodium levels.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for a few hours before the test if it’s part of a larger blood panel. On the day of the test, avoid drinking excessive water or salt if instructed by your doctor.
What Happens During the Test
A healthcare provider will draw blood from a vein in your arm. The blood will be sent to a lab for analysis. The process takes only a few minutes, and you may feel a slight pinch or discomfort, but it’s usually over quickly.
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, nausea, confusion, or even seizures. High sodium levels (hypernatremia) may lead to thirst, dry mouth, rapid heartbeat, or muscle spasms. Doctors use this test to diagnose and monitor conditions like dehydration, kidney disease, or hormonal imbalances that affect sodium balance.
Short name
Sodium Level
Frequently asked questions
What does a normal sodium level mean?
How can I lower my sodium intake if my test shows high sodium?
Can I drink water before my sodium test?
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