Placing the arm cuff correctly on your arm can affect your blood pressure reading. If material such as a long sleeve shirt or sweater sleeve is blocking contact with your skin, your reading may come out up to 50 points higher. If the cuff is too tight, it can affect the accuracy of your reading by about 10 points. Likewise, a cuff too large may cause a lower reading. You can roll up your sleeve, remove your sweater, or change into a short-sleeve shirt to help the blood pressure monitor produce an accurate reading.