The standard way in which blood pressure is to be taken is to be sitting for 5 minutes in a comfortable chair and then the blood pressure should be taken three times approximately 5 minutes apart. There is often variability to the blood pressure and the average of the three measurements is recorded as the blood pressure. The most important measurement is the top number or the systolic blood pressure, although the bottom number or the diastolic blood pressure can be of concern in certain instances. The blood pressure monitor may be need to be calibrated from time to time. A manual mercury manometer is the standard for recording blood pressure, but various automated blood pressure monitors can be accurate in recording blood pressure if the monitors are calibrated from time to time.