Definition of Potassium test:

This test measures the amount of potassium in the blood. Potassium (K+) helps nerves and muscles communicate. It also helps move nutrients into cells and waste products out of cells.

Potassium levels in the body are mainly controlled by the hormone aldosterone.

See also: Aldosterone test

How the test is performed:

A blood sample is needed. For information on how this is done, see: Venipuncture

How to prepare for the test:

The health care provider may tell you to stop taking any drugs that may affect the test.

Drugs that can increase potassium measurements include:

• Aminocaproic acid
• Angiotensin receptor blockers
• Antineoplastic drugs
• ACE inhibitors
• Certain diuretics, called potassium-sparing diuretics
• Epinephrine
• Heparin
• Histamine
• Isoniazid
• Mannitol
• Succinylcholine

Drugs that can decrease potassium measurements include:

• Acetazolamide
• Aminosalicylic acid
• Amphotericin B
• Carbenicillin
• Cisplatin
• Certain diuretics
• Gentamicin
• Insulin
• Laxatives
• Nafcillin
• Penicillin G
• Phenothiazines
• Salicylates
• Sodium polystyrene sulfonate

The following factors can interfere with the test:

• Infusion of potassium-containing fluids
• Infusion of glucose or insulin

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

This test is routinely done as part of a basic or comprehensive metabolic panel.

Your doctor may order this test to diagnose or monitor kidney disease. The most common cause of high potassium levels is kidney disease.

Because potassium is important to heart function, your doctor may order this test if you have signs of high blood pressure or heart problems. Small changes in potassium levels can have a big effect on the activity of nerves and muscles, especially the heart. Low levels of potassium can lead to an irregular heartbeat or other electrical malfunction of the heart. High levels cause decreased heart muscle activity. Either situation can lead to life-threatening heart problems.

It may also be done if your doctor suspects metabolic acidosis (for example, caused by uncontrolled diabetes) or alkalosis (for example, caused by excess vomiting).

Occasionally, the potassium test may be done in persons who are having an attack of paralysis.