Using the correct size is important for an accurate reading. With your arm hanging at the side of your body, measure the circumference of your upper arm at the midpoint between shoulder and elbow. Based on that information, you can determine what size cuff would work for you using the chart below (also available in the instruction manual). You need to use the correct cuff size to ensure an accurate reading. If your cuff is too small, your blood pressure reading will be artificially high. If your cuff is too large, you may get a lower-than-actual reading.
Interchangeability between cuffs All LifeSource units that come with a medium cuff are compatible with the large cuff and vice versa. There is an extra valve in the tubing of the large cuff that allows the cuff to exhaust at the same rate as a medium cuff. If a customer is switching between a medium and large cuff, they must use the tubing that comes with the replacement cuff, as a large cuff will not work with a medium cuff’s tubing, and a medium cuff will not work with the large cuff’s tubing.