Potassium plays an extremely important role in the electrophysiology of your body's cells. According to "Harrison's Principles of Internal Medicine," potassium or K+ is the major positively charged ion in the cells. In fact, approximately 98 percent of the body's potassium stores are found within the cells, located in what is called the intracellular fluid, or the ICF.
Plasma Levels
The normal plasma levels vary between 3.5 and 5.0 millimoles per liter, or mmol/L---a range most commonly used in clinical settings. Other levels can be a little higher, up to 3.7 to 5.2 mmol/L, such as found in the U.S. National Library of Medicine.
The plasma levels represent the delicate balance between the ICF and the extracellular fluid, or ECF. According to "Harrison's Principles of Internal Medicine," the normal ratio of ICF to ECF K+ concentration is 38 to 1. This ratio is important to the resting membrane potential of cells, which is crucial to neuromuscular function.
"The Johns Hopkins Hospital: The Harriet Lane Handbook" states that plasma levels below 2.5 milliequivalents per liter, or mEq/L, produce heart conduction problems and muscular weakness.
Urine Levels
Potassium levels in the urine are helpful in the diagnosis of potassium imbalances. Urine levels, according to "Harrison's Principles of Internal Medicine," are ten- to twenty-fold greater than the K+ levels found in the ECF. The normal values for urine are between 25 and 120 mEq/L per 24 hours. Renal excretion is the major route by which potassium is eliminated from the body.
Stool Levels
Stool elimination of potassium is secondary only to urine excretion. Normal levels of potassium in feces range from 5 to 10 mmol per day per 100 to 200 mL of stool, according to "Harrison's Principles of Internal Medicine." The amount of potassium lost in fecal matter can increase from the normal 10 percent up to 60 percent of dietary intake in kidney conditions such as chronic renal insufficiency.
References
- "Harrison's Principles of Internal Medicine" 17th ed.; Anthony Fauci, M.D., et al., eds.; 2008
- "The Johns Hopkins Hospital: The Harriet Lane Handbook" 17th ed.; Jason Roberston, M.D. and Nicole Shilkofski, M.D.; 2005
- "2007 Current Consult Medicine"; Maxine Papadakis, M.D. and Stephen McPhee, M.D.; 2007
- "BRS: Physiology" 4th ed.; Linda Costanzo, Ph.D; 2007
- "Step-Up to Medicine" 2nd ed.; Steven Agabegi, M.D. and Elizabeth Agabegi, M.D.; 2008
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