An electrolyte test is a blood test that measures if there's an electrolyte imbalance in the body.
Electrolytes are salts and minerals, such as sodium, potassium, chloride and bicarbonate, which are found in the blood. They can conduct electrical impulses in the body.
The test is sometimes carried out during a routine physical examination, or it may be used as part of a more comprehensive set of tests.
For example, your electrolyte level may be checked if you're prescribed certain medications, such as diuretics or angiotensin-converting enzyme (ACE) inhibitors, which are often used to treat high blood pressure.
As well as checking levels of electrolytes in the blood, an electrolyte panel (a group of specific blood tests) can also be used to find out if there's an acid-base imbalance (a normal arterial blood pH range is 7.35 to 7.45).
An electrolyte test can also be used to monitor the effectiveness of treatment for an imbalance that affects how well your organs work.
A value is calculated from your electrolyte test results, called an anion gap. The gap measures if the difference between the electrical charges of your electrolytes is too high or too low.
Treatment for an electrolyte imbalance will depend on which electrolyte is out of balance and by how much. For example, if you have a sodium imbalance you may be advised to lower your salt intake (if sodium is too high) or reduce your fluid intake (if sodium is too low).
Read more about electrolytes and the anion gap on Lab Tests Online UK.
Page last reviewed: 15 March 2022
Next review due: 15 March 2025