Potassium is a mineral that carries a positive charge in the body. The concentration of potassium inside of cells is higher than the concentration outside of cells, and this is important for electrical conduction. The muscles and nerves are very responsive to changing potassium levels. Abnormally high or low levels cause dysfunction, so the body uses numerous mechanisms to keep potassium in the normal range.
Normal Values
The potassium level is most commonly measured from a sample of blood. Most medical laboratories report the normal value of potassium to be 3.5 mEq/L to 5 mEq/L. These values are determined by sampling blood from a large group of people and determining the average and the variation. About 5 percent of people will normally be outside this range.
Regulation
The intestine in the first regulator of potassium. The intestine slowly absorbs potassium so the levels in the blood are less likely to spike too highly. Special potassium-absorbing channels made of protein regulate the uptake. The kidneys excrete excess potassium, or reabsorb potassium if it is too low. This action is coordinated by hormones.
Measurement
Normal potassium numbers can be verified by a number of methods. One technique measures the electrical charge introduced by a blood sample. Another method measures color changes to a solution based on how much potassium is present. When measuring samples, a common source of error is from red blood cells and platelets breaking open and releasing potassium, making the measurement artificially high.
Deviation
Low and high potassium are called hypokalemia and hyperkalemia, respectively. High potassium can be caused by excessive administration of potassium, kidney problems that prevent the filtration of potassium into the urine, and the release of potassium from cells. Low potassium levels can be from inadequate intake, gastrointestinal loss, skin loss, medications, and a shift of potassium into cells.
References
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar, et al.; 2009
- "Harrison's Principles of Internal Medicine"; Anthony S. Fauci, et al.; 2008
- "Physiology"; Linda S.Costanzo; 2008
- "Henry's Clinical Diagnosis and Management by Laboratory Methods"; Richard A. McPherson, et al.; 2006
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