Sodium concentration in serum/plasma
This test measures the amount of sodium, a key mineral, in your blood plasma or serum. Sodium helps regulate fluid balance, nerve and muscle function, and blood pressure.
["Sodium levels help doctors check for dehydration, kidney issues, or conditions like high blood pressure."]
Key facts at a glance
- LOINC
- 111263-0
- Short code
- Sodium Msmt Stl
- Synonyms
- Sodium Msmt Stl
- Category
- electrolyte
- Sample
- stool
- Container
- Clean container
- 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 g
- Stability
- Refrigerated: 24h, Frozen: 7d
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order a sodium test to diagnose or monitor conditions such as dehydration (from vomiting, diarrhea, or excessive sweating), kidney problems, or hormonal imbalances like hyperaldosteronism. It can also help assess fluid shifts in severe illnesses or after certain treatments.
What to Expect Before the Test
No special preparation is usually needed. You may be asked to fast for a few hours before the blood draw, but this depends on your doctor’s instructions. Avoid excessive salt intake 24 hours before testing if advised.
What Happens During the Test?
A healthcare provider will take a small blood sample from a vein in your arm. The sample is sent to a lab for analysis. The test is quick and typically painless, though you may feel a slight pinch during the draw.
What Do 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, confusion, or muscle cramps, while very high sodium (hypernatremia) could lead to thirst, dry mouth, or irregular heartbeat.
Reference range
Adult: 136-145 mmol/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Abnormal sodium levels can signal serious underlying issues. Low sodium often results from excessive water retention, kidney dysfunction, or certain medications. High sodium may indicate dehydration, kidney disease, or overuse of salt or diuretics. Always discuss results with your doctor to understand the full picture.
Short name
Serum Sodium
Frequently asked questions
How long does it take to get my sodium test results?
Can I eat or drink before my sodium test?
What causes sodium levels to be too high or too low?
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 16, 2026. · Read our editorial policy