Electrolytes are minerals in your blood and other body fluids and can be measured by a blood test. Potassium is an electrolyte that is critical to the function of nerve and muscles cells, including those in your heart. The level of potassium in the blood must be maintained within a narrow range. When potassium levels are too high or too low, it can increase the risk of an abnormal heartbeat and have serious consequences, such as a life-threatening rhythm disturbance or even cardiac arrest.

Our body naturally maintains it's own potassium balance within the normal range. 98% of the body's potassium is located inside the cells. Only 2% is located in the blood, outside the cells, which is the part that we measure by a blood test. The potassium stored within the cells can be used by the body to help maintain a constant level of potassium in the blood.

Potassium balance is achieved by matching the amount of potassium taken in with the amount lost. Potassium is taken in through food and electrolyte-containing drinks and lost primarily in urine, although some potassium is also lost through the digestive tract and in sweat. Healthy kidneys are able to adjust the excretion of potassium to match changes in dietary intake. Some drugs and certain conditions affect the movement of potassium into and out of cells, which greatly influences the potassium level in the blood.

Potassium levels, along with other electrolyte levels, are often part of routine blood work, but may be ordered at regular intervals to monitor therapy with certain drugs and in patients with certain chronic diseases. Normal potassium values may vary from lab to lab. In general normal values fall within the following ranges:

A mild decrease in the potassium level in the blood usually causes no symptoms. A more severe decrease can cause muscle weakness, twitches, and even paralysis. Abnormal heart rhythms may develop, especially in people with heart disease. Even mild hypokalemia is dangerous in people taking the heart drug digoxin (Lanoxin)(3)