A low potassium level, or hypokalemia, is a common electrolyte imbalance with a wide variety of causes. Resulting signs and symptoms depend on the severity of potassium depletion and can be easily overlooked if mild. Laboratory tests and electrocardiogram findings can confirm and clarify the extent of depletion in individual cases.
Normal Potassium Levels
Potassium is one of your body's critical electrolytes, and you must maintain circulating blood levels of potassium within a narrow normal range for proper functioning of nerves, muscles and kidneys. The vast majority of your body's potassium is inside the cells, with normal blood levels ranging from 3.5 to 5.3 mEq/L, according to Chemocare. Your body keeps these levels in constant balance by shifting potassium in and out of cells as necessary, and you obtain replacement potassium from your diet. The kidneys excrete any excess potassium in your urine.
Numerous kidney and adrenal gland disorders can lead to hypokalemia, as can medications such as diuretics, certain antibiotics and laxatives. Even if you are otherwise healthy, excessive sweating, diarrhea, vomiting, poor nutrition or rapid weight loss can lead to potassium depletion.
Mild to Moderate Potassium Depletion
Mild hypokalemia, defined as blood levels above 3.0 mEq/L, is often asymptomatic, but if your potassium level drops further, symptoms are more likely to appear. Early symptoms include mild lethargy, weakness, muscle pain and possibly constipation. The risk of heart arrhythmias, or irregular heartbeats, increases with falling potassium levels but can occur even with mild hypokalemia. Laboratory testing confirms a low potassium blood level, which is often accompanied by low magnesium, and changes begin to appear on electrocardiogram tracings when your potassium level falls below 3.0 mEq/L.
Severe Potassium Depletion
When your potassium level falls below 2.5 mEq/L, more serious symptoms and signs begin to develop. Fatigue and weakness increase and you develop muscle cramps, abnormal skin sensations like tingling or burning, decreased reflexes and eventually paralysis. Decreasing muscle activity in your intestines leads to worsening constipation and may result in loss of all bowel activity.
Heart arrhythmias are more likely to occur as are higher blood pressures or a sudden drop of blood pressure when you first sit or stand up. Your kidneys become less efficient at these potassium levels, resulting in changes in urine production, metabolic imbalances and increased thirst. Electrocardiogram changes become more uniformly present and conspicuous.
Recognition and Treatment
Given the broad range of signs and symptoms of hypokalemia, recognizing that you are potassium depleted can be difficult. The presence of an obvious cause, such as crash dieting or an active intestinal illness, can help point you or your health care provider in the right direction. Laboratory measurement of electrolyte levels in the blood and urine, plus an electrocardiogram if indicated, can confirm potassium depletion.
Treatment consists of potassium replacement, often along with magnesium supplements, to help your body correct the imbalance. Oral replacement with potassium-rich fruits and vegetables might be sufficient for mild hypokalemia, but you may require intravenous replacement in more severe or life-threatening situations.
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