In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiological state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the opposite of hypertension, which is high blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood.