When I first received it it read my blood pressure very high. I did it again and the same thing. So that week I had an appt. with my cardiologist and showed it to him and he used it on me. It read so high. He used his blood pressure monitor and it was normal. He used it on both wrists and it was incorrect. Very scary. He told me to send it back immediately and not to use it again. I did this. So sorry it didn't work.