Diastolic blood pressure is the pressure in the arteries when the heart is resting between beats. Blood pressure is measured using two numbers: the systolic pressure (the top number) and the diastolic pressure (the bottom number) . The systolic pressure measures the pressure in the arteries when the heart contracts to pump blood throughout the body, while the diastolic pressure measures the pressure in the arteries when the heart is at rest between beats. Normal blood pressure is a systolic number less than 120 mmHg and a diastolic number less than 80 mmHg. An elevated diastolic blood pressure can be a sign of hypertension and may increase the risk of heart disease, heart attack, and stroke.