Sodium Blood Test
This blood test measures the amount of sodium in your blood to check your body's electrolyte balance and how well your kidneys are working. Sodium is a key electrolyte that helps control fluid levels, nerve signals, and muscle function, and the test is often included in routine metabolic and electrolyte panels.
{"Sodium is a key electrolyte that helps maintain fluid balance and nerve/muscle function","Normal range is typically 136-145 mmol/L","Abnormal levels may indicate dehydration, kidney disease, or other conditions","The test requires a simple blood draw","Results help doctors diagnose and monitor various medical conditions"}
Key facts at a glance
- LOINC
- 2951-2
- Short code
- Na
- Synonyms
- —
- Category
- electrolyte
- Sample
- serum
- Container
- Serum Separator Tube (SST) or Plain Red Top Tube
- Units
- mmol/L
- Ref low
- 136
- Ref high
- 145
- Critical range
- 120 mmol/L – 160 mmol/L
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- ion-selective-electrode
- CPT
- 84295
- SNOMED
- 365797006
- Specimen volume
- 3-5 mL
- Stability
- Room temperature: 72 hours (3 days), Refrigerated (2-8°C): 7 days, Frozen (-20°C or below): 30 days
- Hemolysis max
- 50
- Lipemia max
- 400
- Icterus max
- 60
- TAT
- 1–2 hours
What is this test?
The sodium blood test, also known as serum sodium, measures the concentration of sodium in your blood. Sodium is an essential electrolyte that plays a crucial role in maintaining fluid balance, supporting nerve function, and helping muscles contract properly. This test is part of a routine metabolic panel and electrolyte panel.
Why is it important?
Sodium is one of the most important electrolytes in your body. It helps regulate the amount of water in and around your cells and maintains blood pressure. Your kidneys help control sodium levels by adjusting how much sodium is excreted in urine. When sodium levels are too high (hypernatremia) or too low (hyponatremia), it can indicate underlying health problems.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm using a needle. The sample is then sent to a laboratory for analysis. You do not need to fast before this test, though your doctor may give you specific instructions. The test is quick and generally causes minimal discomfort.
Understanding your results
Normal sodium levels typically range from 136 to 145 mmol/L. Your doctor will interpret your results based on your overall health, symptoms, and other test results. Slight variations from the normal range may not indicate a serious problem, but significant deviations require further investigation.
Reference range
Adult reference range: 136-145 mmol/L. Neonates (0-30 days): 133-145 mmol/L. Children: 136-145 mmol/L. Reference ranges may vary slightly by laboratory methodology and population.mmol/L
No fasting required. Patient should maintain normal fluid intake - avoid overhydration or dehydration before collection. Inform laboratory of any IV fluids received within 4 hours. Certain medications may affect results; consult physician regarding medication timing.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low sodium (hyponatremia) may be caused by certain medications, heart failure, kidney disease, liver cirrhosis, or excessive fluid loss through vomiting or diarrhea. High sodium (hypernatremia) often indicates dehydration, diabetes insipidus, or excessive salt intake. Both conditions can cause symptoms like fatigue, confusion, nausea, or seizures if severe. This test helps diagnose and monitor these conditions, as well as evaluate kidney function and electrolyte balance.
Short name
Na
Part of panels
Frequently asked questions
Do I need to fast before the sodium test?
What happens if my sodium levels are abnormal?
Can medications affect my sodium levels?
How often should I have my sodium checked?
Sources
- 1
- 2
- 3
- 4
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 10, 2026. · Read our editorial policy