Potassium is a positively charged electrolyte, necessary for muscle contraction, pH balance, nerve signal conduction, and action potentials. May be elevated due to renal failure, hypoaldosterone, acidosis, haemolysis, low insulin, hyperglycaemia, exercise. May be decreased due to poor potassium intake, alkalosis, hyperaldosterone, excessive fluid loss, elevated insulin, low magnesium, elevated oestrogen, increased catecholamines.