Blood pressure is a measure of the force that your heart uses to pump blood around your body. It is the pressure of blood pushing against the walls of your arteries. Blood pressure is usually expressed in terms of the systolic pressure (maximum pressure during one heartbeat) over diastolic pressure (minimum pressure between two heartbeats) in the cardiac cycle. Blood pressure is measured in millimeters of mercury (mmHg) and is given as two figures: systolic pressure and diastolic pressure. For example, if your blood pressure is "140 over 90" or 140/90mmHg, it means you have a systolic pressure of 140mmHg and a diastolic pressure of 90mmHg. Ideal blood pressure is considered to be between 90/60mmHg and 120/80mmHg, while high blood pressure is considered to be 140/90mmHg or higher. Low blood pressure is considered to be below 90/60mmHg. Blood pressure is one of the vital signs that healthcare professionals use in evaluating a patients health, along with respiratory rate, heart rate, oxygen saturation, and body temperature. High blood pressure, also called hypertension, is blood pressure that is higher than normal and can increase the risk of developing serious long-term health conditions, including coronary heart disease. Low blood pressure is less common and can be caused by a number of underlying conditions, including heart failure and dehydration.