Potassium is an electrolyte that is vital to cell metabolism. It helps transport nutrients into cells and removes waste products out of cells. It is also important in muscle function, helping to transmit messages between nerves and muscles. This test measures the amount of potassium in the blood and/or urine. Electrolytes are minerals that carry a charge and exist in your body fluids. Potassium and other electrolytes such as sodium, chloride, and bicarbonate (total CO2) help regulate the amount of fluid in the body and maintains a stable acid-base balance. Potassium is present in all body fluids, but most potassium is found within the cells. Only a small amount is present in fluids outside the cells and in the liquid part of the blood (called serum or plasma). We get most of the potassium we need from the foods that we eat. Most people will have an adequate intake of potassium. The body uses what potassium it requires, then the kidneys eliminate the rest in the urine. The body tries to keep the blood potassium level within a very narrow range. Levels are mainly controlled by aldosterone, a hormone produced by the adrenal glands above the kidneys. Because the blood concentration of potassium is so small, minor changes can have significant health effects. Potassium levels that are too low or too high can alter the function of the nerves and muscles and there can be serious health complications, such as shock, breathing problems (respiratory failure), irregular heart beat, or the heart muscle may even lose its ability to contract. Measuring potassium as part of an electrolyte or metabolic panel may help diagnose an electrolyte imbalance or acidosis or alkalosis. Acidosis and alkalosis describe the abnormal conditions that result from an imbalance in the pH of the blood caused by an excess of acid or alkali (base). This imbalance is typically caused by some underlying condition or disease.