The company sent letters to some users of the FreeStyle Libre readers on February 13. People with diabetes use glucose monitors to check their blood sugar levels because of problems with how their ...

The problem involves only the reader, not the sensor that the person wears on their arm.

The FreeStyle Libre is a blood glucose monitor that doesn’t require blood samples or finger sticks. The readings are based on a sensor on your arm continuously for up to 14 days at a time.

The monitor used with the FreeStyle Libre line uses lithium-ion batteries similar to those in a mobile phone.