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Also known as: K
Formal name: Potassium

The Test Sample

What is being tested?

This test measures the amount of potassium in the blood. Potassium is an electrolyte that is vital to cell metabolism and muscle function. Potassium, along with other electrolytes such as sodium, chloride, and bicarbonate (total CO2), helps regulate the amount of fluid in the body, stimulates muscle contraction, and maintains a stable acid-base balance. Potassium is present in all body fluids, but most potassium is found within your cells. Only about 2% is present in fluids outside the cells and in the liquid part of the blood (called serum or plasma). Because the blood concentration of potassium is so small, minor changes can have significant consequences. If potassium levels are too low or too high, there can be serious health consequences; a person may be at risk for developing shock, respiratory failure, or heart rhythm disturbances. An abnormal potassium level can alter the function of neuromuscular tissue; for example, the heart muscle may lose its ability to contract.

How is the sample collected for testing?

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

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.