Hi. There are many reasons why gamma-glutamyltransferase (GGT) might be elevated. The most likely is a problem with bile ducts in the liver. Corticosteroid medications can also raise GGT levels, as can drugs given to control epilepsy (phenobarbital), so I am assuming your dog is not on any of these. Your vet should be undertaking further tests to rule out any problems with the liver first ... if they have chosen not to do this, then you should ask why? And if they don't give you a very good answer, change your vet.