Sodium Test
Also known as: Na, Serum Sodium
What is Sodium?
Sodium is an essential electrolyte that regulates fluid balance, blood pressure, and nerve and muscle function.[MedlinePlus (NIH)]
What This Test Measures
This test measures the level of sodium in your blood. Sodium is tightly regulated by the kidneys and hormones.[Mayo Clinic]
Why It's Important
Sodium imbalances can cause serious symptoms affecting the brain, heart, and muscles.[MedlinePlus (NIH)]
Sodium levels help diagnose dehydration, kidney disease, heart failure, and hormonal disorders.[Cleveland Clinic]
Who Should Get This Test?
Sodium is routinely measured as part of basic metabolic panels.
Risk Factors
- Routine health screening (part of BMP or CMP)
- Dehydration or excessive fluid intake
- Taking diuretics or other medications affecting sodium
- Heart failure
- Kidney disease
- Liver disease with fluid retention
- Confusion, seizures, or altered mental status
- Diabetes insipidus
- Adrenal insufficiency
- Severe vomiting or diarrhea
Screening Schedule
Included in routine annual bloodwork. Frequent monitoring for patients on diuretics, with heart/kidney failure, or hospitalized patients.
What Happens During the Test
A blood sample is drawn from a vein in your arm. Sodium is typically part of a basic or comprehensive metabolic panel.
Duration
5 minutes for the blood draw; results usually available within hours
Discomfort Level
Minimal - brief pinch from needle insertion
Risks & Side Effects
Sodium testing through blood draw carries very few risks.
- •Minor pain or bruising at the needle site
- •Slight bleeding
- •Rarely, lightheadedness
- •Very rare risk of infection
Normal Range
136 to 145 mEq/L.
Note: Even small deviations from normal can cause symptoms.
Source: MedlinePlus (NIH)Unit Conversion
Convert between mEq/L and mmol/L
| mEq/L | mmol/L |
|---|---|
| 125 | 125 |
| 130 | 130 |
| 136 | 136 |
| 140 | 140 |
| 145 | 145 |
| 150 | 150 |
High Values
High sodium (hypernatremia) causes thirst, confusion, and muscle twitching. Causes include dehydration, diabetes insipidus, and excessive salt intake.[Mayo Clinic]
Low Values
Low sodium (hyponatremia) causes headache, confusion, nausea, and in severe cases, seizures. Causes include excess water intake, heart failure, and SIADH.[Mayo Clinic]
Test Limitations & Accuracy
Sodium interpretation requires clinical context.
- ⚠Pseudohyponatremia: falsely low with high lipids or proteins
- ⚠IV fluid administration affects levels
- ⚠Must interpret with fluid status (dehydrated vs overloaded)
- ⚠Acute vs chronic hyponatremia have different implications
- ⚠Blood glucose affects sodium (corrected sodium calculation needed)
- ⚠Medications cause many sodium abnormalities
- ⚠Posture affects levels slightly
Alternative & Complementary Tests
Sodium is interpreted with other electrolytes and kidney function.
To determine cause of sodium abnormality
To assess kidney handling of sodium
Often abnormal alongside sodium
To assess kidney function
For suspected SIADH
For suspected adrenal insufficiency
References
Medical Disclaimer
This information is for educational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for interpretation of test results and medical decisions.
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