If this isn't happening just in the morning (when they have an empty stomach), she needs to see a vet.
It could be pancreatitis but every Yorkie should probably be bile acid tested anyway, so there is no harm in looking.
I gave Ellie Innova canned (36% fat dry matter) before her bile acid test and 5 days later she had pancreatitis. It may have been the food...I don't know.
I would get a blood panel done to look at amylase and lipase (could be elevated if pancreatitis) and a bile acid test.
__________________ Crystal  , Ellie May (RIP)  , Rylee Finnegan  , and Gracie Boo🐶 |