It works, but you can practically make a sandwich while you wait for your reading. It's slow. I'd say it averages 6-7 seconds to read. And I've had readings vary by 3% just a second later. So it's not the most accurate thing, but works well enough that you could monitor your oxygen and pulse and notice anything you should bring to your doctor's attention. For example, if you get three readings in a row of 92%, or your resting heart rate is always over 100, mention that to your doctor. The blue cSee full review