The heart uses a pumping mechanism to send blood into the arteries (ART-er-eez) and throughout the body. This pumping, together with arterial (art-EAR-ee-all) resistance to the blood flow, creates a specific level of pressure in those vessels. Blood pressure is measured by recording the pressure during both phases of the heart's pumping: the systolic (sis-TALL-ik) or active beating phase, and the diastolic (DY-ah-stall-ik) or resting phase. High blood pressure or hypertension (hy-per-TEN-shun) refers to the condition when the force of the blood in the vessels is greater than an accepted standard. For an adult, high blood pressure is defined by a systolic pressure greater than or equal to one hundred and forty, and a diastolic pressure over 90. Beyond this, the extent of a person's high blood pressure is categorized into one of four levels, from mild to very severe. In most cases, the cause of this condition is not identifiable, and there are seldom any noticeable physical symptoms. Generally, however, a physician may check for underlying problems that can lead to high blood pressure. For example, if the heart is pumping harder than normal due to heart disease, blood pressure may go up. Or if the major arteries become stiff, narrow, or hardened due to age or arterial disease, pressure can increase due to blood being pumped through a smaller-than-normal vessel. Another potential cause of high blood pressure is an increase in blood volume due to the addition of more fluid to the system. This can occur when the kidneys malfunction. Once hypertension has been diagnosed, a physician will generally monitor the patient frequently, may prescribe medication to lower blood pressure, and will often suggest diet and exercise changes. If you're concerned about your blood pressure, or have questions about high blood pressure, contact a healthcare provider.