Potassium is a mineral necessary for nerve and muscle functioning, particularly the muscles of the heart. Low levels of potassium, called hypokalemia, occur for many reasons. Normal blood levels of potassium range between 3.5 and 5.0 milliequivalents per liter, or mEq/L, according to Gale Encyclopedia of Medicine . Levels between 3.0 and 3.5 or below are considered mild hypokalemia; levels between 2.5 and 3.0 are considered moderate. Usually, levels of 3.0mEq/L are not dangerous in healthy people; symptoms normally don't appear until levels fall below 3mEq/L, Stanford University says.
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People with certain health issues are more likely to develop symptoms, even at potassium levels of 3mEq/L. People who have heart disease such as heart failure, left ventricular hypertrophy -- an enlargement of the left pumping chamber of the heart -- or decreased blood flow, known as cardiac ischemia, are more likely to develop symptoms with mild to moderate levels of hypokalemia. Alcoholics are also more likely to have symptoms with mild to moderate drops in potassium levels. Prescription diuretics are the most common cause of hypokalemia; as many as between 10 percent and 40 percent of people taking thiazide diuretics have hypokalemia, F. John Gennari, M.D. of the University of Vermont School of Medicine reported in the August 1998 issue of the New England Journal of Medicine.
Symptoms of hypokalemia include leg cramps, constipation, muscle discomfort, confusion and weakness. Symptoms such as irregular heartbeat do not normally occur until levels fall to 2mEq/L or less, but cardiac symptoms are rare in people who don't have cardiac disease, Dr. Gennari says. Changes in the electrocardiogram can start when levels fall to 3mEq/L, with flattening of T-waves, ST segment depression and more pronounced U waves. Paralysis that can starts at the feet and moves upward, eventually resulting in respiratory difficulty, can develop at the same level.
A diagnosis of hypokalemia is made on the basis of laboratory results. not symptoms. A doctor draws a blood sample from a vein for the test. An EKG helps diagnose potentially harmful irregularities in the heartbeat.
Mild hypokalemia may not require treatment. Increasing dietary intake of potassium with foods such as bananas, milk, peanut butter, oranges and tomatoes may help. At levels of 3mEq/L, oral potassium supplements usually supply adequate treatment. When levels fall below 2.5mEq/L, intravenous potassium administration may be necessary.