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Testing sodium, potassium and more

An electrolyte test is used to identify problems with the body's electrolyte ( salt) balance.

Electrolytes are minerals that are found in body tissues and blood in the form of dissolved salts. They help to move nutrients into cells in the body and move waste products out of them. Electrolytes also maintain a healthy water balance and help stabilise the body's acid/base (pH) level.

The main electrolytes in the body are potassium and sodium. Other electrolytes are chloride and bicarbonate.

Potassium is found mainly inside the body's cells. Small amounts are also found in blood plasma. It has an important role in regulating the heart's rhythm and ability to contract.

Sodium is mainly found outside cells where it helps regulate the amount of water in the body.

Why is electrolyte testing carried out?

Electrolyte testing may be carried out as part of routine blood tests, called U+Es.

You may be tested if your GP thinks you have an imbalance of one of the electrolytes (usually sodium or potassium), or if an acid-base (pH) imbalance is suspected.

The test is useful in evaluating cases where kidney disease, high blood pressure or heart failure is suspected and in monitoring the effectiveness of treatment.

Electrolytes may also be checked if you are prescribed certain medication, particularly diuretics or ACE inhibitors (used to treat high blood pressure and heart failure).

How is electrolyte testing carried out?

A blood sample is taken from a vein in the arm.

WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on February 24, 2017

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