Serum/plasma sodium and potassium concentration measurement
This test measures the levels of sodium and potassium in your blood, two key electrolytes that help balance fluids and support nerve and muscle function.
["Electrolyte balance is critical for heart rhythm, muscle function, and fluid regulation."]
Key facts at a glance
- LOINC
- 34548-8
- Short code
- Sodium + Potassium Pnl SerPl-sCnc
- Synonyms
- Sodium + Potassium Pnl SerPl-sCnc
- Category
- electrolyte
- Sample
- serum
- Container
- Red-top tube (SST)
- 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 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 Is Done
Doctors may order this test to check for electrolyte imbalances, monitor conditions like high blood pressure, heart disease, kidney problems, or certain medications that affect sodium or potassium levels. It can also help diagnose symptoms such as muscle weakness, confusion, irregular heartbeat, or excessive thirst.
What to Expect Before the Test
No special preparation is needed. You may be asked to fast for 8–12 hours before the test if it involves a blood draw, but this is not always required for electrolyte panels. Bring any medications or supplements you’re taking, as they may affect results.
What Happens During the Test
A healthcare provider will draw blood from a vein in your arm. The blood sample is then sent to a lab for analysis. Results are typically available within 24–48 hours, depending on the lab.
Possible Results and Interpretation
Results are compared to standard reference ranges for sodium and potassium. Abnormal levels can indicate conditions like dehydration, kidney disease, heart problems, or certain medications (e.g., diuretics, heart medications). Your doctor will discuss findings with you.
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.
Serum sodium and potassium levels are vital for maintaining fluid balance, nerve function, and muscle contractions. Low sodium (hyponatremia) can cause confusion, seizures, or irregular heartbeat, while high sodium (hypernatremia) may lead to swelling, muscle cramps, or kidney damage. Low potassium (hypokalemia) can weaken muscles, cause heart arrhythmias, and high potassium (hyperkalemia) may lead to dangerous heart rhythms. Imbalances are often treated with diet, fluids, or medications.
Frequently asked questions
What causes sodium or potassium levels to be too high or too low?
How long does it take to get results?
Can I eat or drink before this 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 16, 2026. · Read our editorial policy