Electrolyte blood test

What does the Electrolytes measure?

An electrolyte panel measures sodium, potassium, chloride and bicarbonate, and can include the anion gap and osmolality.

Why is the Electrolytes ordered?

It is ordered to check hydration, kidney function, and the effect of medications on the body's salt balance.

Tests in this panel

Each test links to its own page with named reference-range sources.

Sources: [CLSI]

• SodiumSodium is the main salt in your blood and body fluids. It controls your water balance, helps set your blood pressure, and keeps your nerves and muscles working. This test measures your level.
• PotassiumPotassium is the main mineral inside your cells. Your body needs it to keep a steady heartbeat, move your muscles, and pass nerve signals. This test measures your level.
• ChlorideChloride is the main negatively charged electrolyte (a mineral carrying an electrical charge) in blood. It follows sodium to hold fluid in the right places and swaps with bicarbonate to steady acidity; the test measures its concentration.
• BicarbonateBicarbonate is the main chemical buffer in blood, neutralising acid so pH stays in a narrow range. Your lungs adjust it by releasing carbon dioxide and your kidneys by holding or dumping it; the test measures the amount present.
• Anion GapThe anion gap is a calculation, subtracting measured negative electrolytes from positive ones. The leftover difference estimates unmeasured acids and charged particles the standard panel does not detect directly.
• Serum OsmolalitySerum osmolality counts the total dissolved particles packed into a fixed volume of blood, chiefly sodium, glucose, and urea. That particle count tracks the ratio of water to solutes across your whole system.

Frequently asked questions

What is included in the Electrolytes?

An electrolyte panel measures sodium, potassium, chloride and bicarbonate, and can include the anion gap and osmolality. It typically reports 6 results: Sodium, Potassium, Chloride, Bicarbonate, Anion Gap, Serum Osmolality.

Why is the Electrolytes ordered?

It is ordered to check hydration, kidney function, and the effect of medications on the body's salt balance.

How should the Electrolytes be read as a whole?

No single value tells the full story — the results are read together, and each value is compared against the reference range printed on your own report, which can vary by lab, method and equipment.

Do the reference ranges in the Electrolytes vary between labs?

Yes. Ranges depend on the laboratory's equipment and method, so the range printed on your own report is the one that applies to your result. Each test page names the standards body behind its range.