Hypokalemia is a decrease in plasma potassium levels below 3.5 mmol/L (mEq/L). The main cause of this condition is excessive loss of potassium through the kidneys or gastrointestinal tract. Symptoms include general muscle weakness, increased urination. The greatest danger is the development of cardiac arrhythmias. In addition to determining the concentration of potassium in the serum, the diagnostic search should be aimed at establishing the cause of the electrolyte imbalance. For treatment, potassium deficiency is replenished and the pathology that caused it is treated.