Electrolyte measurements are used to screen for an electrolyte or pH imbalance and to monitor the effect of treatment on a known imbalance that is affecting bodily organ function. Since electrolytes are often abnormal in a variety of acute and chronic illnesses, they are frequently requested in hospitalised patients.

It may be requested as part of routine testing or as a diagnostic aid for a specific disorder, such as oedema or cardiac arrhythmias. If one or more of the electrolytes is imbalanced, your doctor may want to monitor that individual electrolyte closely while treating the cause of the imbalance.

Electrolyte levels are affected by how much is taken in through your diet, the amount of water in your body, and the quantity of electrolytes excreted by your kidneys. They are also affected by hormones, especially aldosterone, a hormone that retains sodium in the body but increases the loss of potassium.

In specific disorders, one or more electrolytes may be abnormal. Your doctor will look at the overall balance but is likely to be especially concerned with your sodium and potassium levels. People whose kidneys are not functioning properly, for example, may retain excess fluid in the body, diluting the sodium and chloride so that they fall below normal concentrations. Those who experience severe fluid loss may show an increase in K⁺, Na⁺, and Cl^- (Cl^- tends to mirror the Na⁺). Some forms of heart disease, muscle and nerve problems, and diabetes may also have one or more abnormal electrolytes.

Knowing which electrolytes are out of balance can help your doctor determine the cause and treatment to restore proper balance. If left untreated, electrolyte imbalance can lead to dizziness, cramps, irregular heartbeat, and possibly death.

Test results are reported as a numerical value and must be compared with an appropriate reference range in order to determine the significance of the result. Reference ranges may vary for a variety of reasons including the patient's age and sex, as well as the instrumentation or kit used to perform the test. To learn more about reference ranges, please see the article, Reference Ranges and What They Mean. Your local laboratory will advise your doctor of the appropriate reference range for your particular test.

Depending on which electrolyte(s) is out of balance and the extent of that change, treatment may involve changing your diet, for example to lower salt intake, increasing or reducing fluid intake, or taking or stopping medication such as diuretics. Once treatment has begun, you may be asked to have regular testing to determine how well the treatment has worked and to make sure the imbalance does not reoccur.