BMI testing is used to check if your weight is within range for your height. Although this test is often used to check if you are within the commonly accepted ranges of weight, it's not perfect. This is due to differences in body frames, metabolic rates, age groups, and a lifestyles. Most importantly, we should be healthy, full of energy and happy no matter what our current BMI reading. It can be equally bad to have too low a BMI reading as a high reading.