We talk a lot about the top number when it comes to blood pressure, but the bottom number is important as well. The top number (systolic blood pressure) refers to the blood pressure when the heart is contracting. The bottom number (diastolic blood pressure) refers to the blood pressure when the heart is relaxing, which is why this number is typically lower than the top. The target for the lower number is below 80, however, blood pressure targets can depend on your age and other factors so speak to your doctor to determine what your blood pressure targets should be. Low diastolic pressure can be a concern if it is associated with dizziness or lightheadedness. The diastolic number can drop with certain medications, dehydration and with stiffening of arteries as we age. Speak to your doctor if you have concerns about your diastolic blood pressure.