Electrolytes (Sodium, Potassium)
Also known as: Serum electrolytes, Na K test, U&E, electrolytes test, sodium potassium test, namak ki kami test
Measures sodium, potassium, chloride and bicarbonate in the blood. These salts control body water, nerves, muscles and the heart rhythm.
Why it's ordered
With vomiting, diarrhoea, dehydration, weakness or confusion; with kidney or heart disease; and when taking medicines such as water tablets (diuretics) or some blood pressure drugs.
Preparation
No fasting needed.
Typical adult values
| Sodium (Na) | about 135–145 mmol/L |
|---|---|
| Potassium (K) | about 3.5–5.1 mmol/L |
| Chloride (Cl) | about 98–107 mmol/L |
| Bicarbonate (HCO₃) | about 22–29 mmol/L |
Ranges vary between labs and methods. Always use the range printed on your report.
If it's high
High sodium usually means dehydration. High potassium can be caused by kidney disease or some medicines and can affect the heart rhythm, so very high values need urgent care.
If it's low
Low sodium can follow vomiting, diarrhoea, heart or liver disease, or some medicines, and severe cases can cause confusion. Low potassium often follows diarrhoea, vomiting or water tablets and can cause weakness and cramps.
Good to know
A falsely high potassium is common if the blood sample is damaged (haemolysed) or delayed, so an unexpected high potassium is often repeated before any treatment. Severe diarrhoea in children needs ORS and medical advice.
Common questions
What is a normal sodium and potassium level?
Typically sodium about 135–145 mmol/L and potassium about 3.5–5.1 mmol/L. Always use the range printed on your report.
Why is my potassium high when I feel fine?
A falsely high potassium is common if the blood sample is damaged (haemolysed) or delayed, so an unexpected high potassium is often repeated before any treatment.
What causes low potassium?
Low potassium often follows diarrhoea, vomiting or water tablets and can cause weakness and cramps.
Is high potassium dangerous?
It can affect the heart rhythm, so very high values need urgent care.