Blood pressure, abbreviated clinically as BP, systolic blood pressure (SBP) and diastolic blood pressure (DBP), is a very important vital sign and is often measured to assess the stability of a patient’s current status when measuring whether he or she is critically ill. The standard range for systolic blood pressure is 100-120 mm Hg and for diastolic blood pressure is 60-80 mm Hg. To further assess whether a patient has abnormal blood pressure, it is often recommended in clinical practice to combine ambulatory blood pressure monitoring to assess the overall blood pressure fluctuations over 24 hours and to grasp the pattern of blood pressure changes. In the case of hypertensive patients, these tests can also help in the development of appropriate medication regimens.