The Mayo Clinic says that normal blood levels of potassium range from 3.6 to 4.8 milliequivalents per liter (mEq/L). Proper potassium levels are critical to the function of the nerves and muscles, especially the heart. Potassium levels that fall slightly below normal can cause heart flutters or palpitations that generally are not serious. Medically significant changes in the level of potassium are an emergency because of the potential for abnormal heart rhythms that can be fatal.
Potassium
Potassium is a vital mineral in the body because it acts as an electrolyte--a substance that donates ions to conduct electrical impulses--that controls the firing of nerves and the contraction of muscles. When potassium levels fluctuate too far out of the normal range, muscle function suffers. The coordinated contraction of the heart, a tightly regulated muscle that pumps blood through the body, malfunctions when potassium levels change drastically.
Role of Potassium
The movement of sodium and potassium across cell membranes sets up an electrical current that allows coordinated firing of a muscle along its entire length. For the heart, this means that the heartbeat is coordinated to squeeze the blood rhythmically out into circulation. An imbalance in sodium or potassium levels produces a faulty electrical current that disrupts coordinated beating of the heart. When sections of the heart beat out of rhythm, it can cause the sensation of heart flutters or more serious arrhythmias.
Regulation
Oregon State University recommends a daily intake of 4.7 mg of potassium per day for optimal health. Most people maintain potassium levels in a healthful range without needing to worry about dietary intake levels. Problems with potassium usually stem from medical conditions or medications that cause the body to excrete or retain too much potassium. Some high blood pressure medications significantly increase potassium levels, while others decrease potassium levels.
High Potassium
Hyperkalemia refers to an excess of potassium in the blood, above 6.0 mEq/L, according to the Mayo Clinic. Hyperkalemia causes muscle weakness or even temporary paralysis and tingling in the hands and feet. Hyperkalemia can wreak havoc on the coordinated beating of the heart, and the resulting arrhythmias can send the patient into cardiac arrest.
Low Potassium
Levels of potassium slightly lower than normal can cause generally harmless heart flutters. The Mayo Clinic defines medically significant low potassium, or hypokalemia, as less than 2.5 mEq/L of potassium in the blood. The University of Maryland says that hypokalemia usually does not result from a poor diet. Instead, dehydration from vomiting or diarrhea or use of diuretic blood pressure medications can force too much potassium out of the body, resulting in hypokalemia. Symptoms include weakness and stomach cramps. The most dangerous effect of hypokalemia is cardiac arrhythmia. In the absence of adequate levels of potassium, just as with excess potassium, the heartbeat becomes uncoordinated. The arrhythmia can cause cardiac arrest.
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