Electrolytes Test
A blood test measuring the body's salts: sodium, potassium, chloride and bicarbonate.
Quick Summary
To check for imbalances from dehydration, vomiting, kidney problems or medicines.
Sodium, potassium, chloride and bicarbonate.
No special preparation.
Overview
Electrolytes keep fluids, nerves and muscles, including the heart, working properly.
They're checked often in hospital and with diuretics or kidney disease.
What It Measures
Sodium
Fluid balance.
Potassium
Heart and muscle function.
Chloride and bicarbonate
Acid-base balance.
How It's Performed
- 01
Preparation
Usually no special preparation. Tell the staff about medicines you take.
- 02
Blood sample
A small amount of blood is taken from a vein in your arm with a thin needle.
- 03
Afterwards
Press on the spot for a minute. A small bruise is common; you can go back to normal activities.
Reference Ranges
Note: Normal ranges vary by laboratory. Consult your report for the specific reference used.
| Parameter | Typical Range (Adult) | Units |
|---|---|---|
| Sodium | 135–145 | mmol/L |
| Potassium | 3.5–5.0 | mmol/L |
| Chloride | 98–107 | mmol/L |
| Bicarbonate | 22–29 | mmol/L |
Interpreting Results & Next Steps
Discuss with Doctor
Normal ranges differ between laboratories, ages and sexes; always use the range printed on your report and ask your doctor what your results mean.
If values are Low:
Low sodium can cause confusion; low potassium can cause weakness and heart rhythm problems.
If values are High:
High potassium can affect the heart and may need urgent treatment.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Electrolyte Panel(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Electrolyte test(opens in a new tab) · NHS