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Purchase a blood pressure monitor. Set up to check your blood pressure. Position yourself properly.
If you are checking your blood pressure at home, purchase an automatic cuff-style monitor. This can help give you the most accurate readings of your pressure in addition to being more simple to use than aneroid sphygmomanometers, which is the technical name of hand-employed blood pressure monitors.  A digital or automatic monitor has a cuff that inflates at the push of a button and requires no real work from you. This is probably your easiest option if you are monitoring your blood pressure from home. Choose a monitor that is validated and approved by an international organization such as the Association for the Advancement of Medical Instrumentation, the British Hypertension Society and the International Protocol for the Validation of Automated BP Measuring Devices.  Make sure the monitor is properly calibrated — talk to your doctor or a medical supply store about calibration. If you have special needs, such as being elderly or pregnant, make sure to choose a monitor specifically suited to your purposes.  Make sure the cuff fits your arm by measuring the width around your bicep. Most companies make different sizes, which will help you get the most accurate reading possible. Too small of a cuff can cause false elevated readings, too large of a cuff can give false low blood pressure readings. You can buy blood pressure monitors at many pharmacies and most medical supply stores. Your insurance company may cover the cost if you’re using the device to manage a medical condition. Make sure you can return or exchange if the apparatus doesn't work or malfunctions. There are many factors that can affect your blood pressure reading. Preparing yourself for your monitoring test can give the most accurate readings. In preparation for your test:  Avoid testing right after you wake up. Avoid eating or drinking anything for 30 minutes before testing. Avoid caffeine and tobacco for 30 minutes before testing. Avoid exercising for 30 minutes before testing, even if it’s light walking. Empty your bladder.  Make sure to read the device instructions before you do any testing. Before and during the test, it’s important that you position your body and arm properly. Sitting quietly and in a supported, upright position can help you get the most accurate reading.  Sit down and relax for at least 30 minutes before you test your pressure.  Do your best to not move or talk during the actual testing.  Sit with your back straight and supported, such as in a dining room chair. Keep your feet flat on the floor and don’t cross your legs.  Support your bare arm on a table, desk, or the arm of a chair. Your arm should rest at the level of your heart, for which you might need a pillow or cushion to prop it up.  The cuff should be directly above the eye, or crook, of your elbow.