What is the cause of low electrolyte potassium? Let’s first understand that the normal range of potassium values is between 3.5 mmol/L and 5.5 mmol/L. Usually when our serum potassium is below 3.5 mmol/L, we call it hypokalemia. What causes low blood potassium? The first one is a reduced intake of potassium. For example, in patients with gastrointestinal obstruction, coma, prolonged fasting after surgery, or in those who do not eat for a long time to lose weight, hypokalemia can occur. Secondly, we have too much potassium excretion. The first one is the gastrointestinal excretion of potassium. For example, diarrhea, vomiting, and potassium loss through the kidneys, kidney disease, and some potassium loss through the skin, so that a lot of sweating.