Hypokalemia, also spelled hypokalaemia, is when blood’s potassium levels are too low. Potassium is an important electrolyte for nerve and muscle cell functioning, especially for muscle cells in the heart.
Normal potassium levels are between 3.5 and 5.0 mmol/L (3.5 and 5.0 mEq/L) with levels below 3.5 mmol/L defined as hypokalemia. Mildly low levels do not typically cause symptoms. Symptoms may include feeling tired, leg cramps, weakness, and constipation. It increases the risk of an abnormal heart rhythm such as bradycardia and cardiac arrest.
Causes of hypokalemia include diarrhea, medications like furosemide and steroids, dialysis, diabetes insipidus, hyperaldosteronism, hypomagnesemia, and not enough intake in the diet. It is classified as severe when levels are less than 2.5 mmol/L. Low levels can also be detected on an electrocardiogram (ECG). Hyperkalemia refers to a high level of potassium in the blood serum.
The speed at which potassium should be replaced depends on whether or not there are symptoms or ECG changes. Mildly low levels can be managed with changes in the diet. Potassium supplements can be either taken by mouth or intravenously. If given by intravenous, generally less than 20 mmol are given over an hour. High concentration solutions (>40 mmol/L) should be given in a central line if possible. Magnesium replacement may also be required.
Hypokalemia is one of the most common water–electrolyte imbalances. It affects about 20% of people admitted to hospital. The word "hypokalemia" is from hypo- means "under"; kalium meaning potassium, and -emia means "condition of the blood".