This machine only has a self life of 30 days. The product is so horrible, overstock will only gurantee it for 30 days. I can't believe overstock has a product like this. It will read the correct blood pressure for the first couple of times then it starts going hairwire. My doctor told me it was a piece of junk and I should return it immediately. Overstock would not honor this return. I am very displeased with overstock and this product. My advice is to STAY AWAY!!!!