Potassium is the most represented intracellular electrolyte in the human body. Its extracellular levels are maintained within strict limits through different mechanisms, which constitute the homeostasis of potassium. Hyperkalemia is the most common electrolyte disorder in patients with cardiovascular disease. Although with different levels of severity, it carries an increased risk of hospitalization, cardiovascular morbidity and mortality. Hyperkalemia may also be an important cause of discontinuation or impossibility of titration of fundamental therapies in the cardiology patient. The principal aim of this review is to analyze the mechanisms underlying hyperkalemia, as well as to summarize its epidemiology, risk factors, monitoring methodologies and electrophysiological and electrocardiographic effects, providing just only few essential elements of therapy. In this way the physician, and especially the cardiologist, can have an adequate knowledge for its management in clinical practice.