The blood pressure machines that you can use free of charge in many grocery stores and drugstores may have been accurate when first installed. But in order to stay accurate, they must be maintained and recalibrated. Generally, no information is available regarding the care of these devices. As a result, the reading you get has limited value because it may be incorrect. It's best to have your blood pressure checked in a medical facility or in a community screening program with trained staff.
July 17, 2012