Medical identification tag

A medical identification tag is a small emblem or tag worn on a bracelet, neck chain, or on the clothing bearing a message that the wearer has an important medical condition that might require immediate attention. For emergency medical providers such as paramedics and emergency physicians, medical identification tags are particularly useful in situations where the wearer is unconscious, altered mental status, very young, or otherwise unable to provide critical medical information.

Source: Wikipedia — Medical identification tag (CC BY-SA 4.0)