If you use a cuff that is too small, the resulting blood pressure reading will be too high. And if you use a cuff that is too large, the resulting blood pressure reading will be too low. This is very serious in the sense that if the cuff is too small, you will be incorrectly diagnosed with high blood pressure. As a result, you will be taking in medications which may have negative effects on your body. On the other hand, if your blood pressure is high and goes undiagnosed because of the use of large cuff, it may lead to damage blood vessels, stroke and heart attack. It is advisable to insist on the correct cuff size to your arm when your blood pressure is being checked.