Potassium is an essential ion found within the cells of the body. The delicate balance between potassium outside the cell, known as the extracellular fluid K+ and the potassium inside the cell, called the intracellular fluid K+ helps maintain the electrophysiology of the body.
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Crucial to neuromuscular function, potassium levels are regulated by the acid-base balance within the blood, kidney filtration, dietary intake, gastrointestinal absorption and elimination through stool.
Blood Potassium Levels
Normal blood potassium levels can range from 3.5 to 5.2 millimoles per liter or mmol/L, according to "2007 Current Consult Medicine." Total body potassium stores are approximately 50 milliequivalents per kilogram of body weight or mEq/kg. More than 95 percent of the body's potassium is stored in the ICF.
If potassium is forced out of the cells causing the level to rise above 5.2 mmol/L then a condition known as hyperkalemia occurs. Hyperkalemia can result in dangerous arrhythmias and cardiac arrest.
If the potassium is forced inside the cell and the value drops below 3.0 mmol/L, then it is called hypokalemia. Low potassium levels lead to muscular weakness, fatigue, cardiac electrical problems and constipation due to ileus.
Urine Potassium Levels
Urine excretion can be 1 to 110 percent of the potassium load, depending on aldosterone levels, acid-base status and dietary intake, according to "BRS: Physiology" authored by Linda Costanzo, Ph.D. The major mode of potassium elimination from the body, the nephron of the kidney filters and excretes 10- to 20-fold the amount of potassium found in the ECF. The normal range of urine potassium is 25 to 120 mEq/L per every 24-hours.
Fecal Potassium Levels
The normal dietary intake, according to "Harrison's Principles of Internal Medicine" ranges from 40 to 120 mmol per day. That is approximately 1 mmol per kilogram of weight per day. The gastrointestinal tract absorbs 90 percent of that intake, excreting at least 5 to 10 mmol/d in a volume of 100 to 200 ml. The levels of absorption and excretion can be affected by diarrhea, abuse of laxatives, chronic renal problems and malabsorption conditions.