Business manager Paul Bonini said it now employed five vets, up from three, and the building was "struggling to cope" with the volume of work.
The refit will focus on the waiting area, the surgery and consultation rooms and work is expected to be completed in four stages, hopefully by July 19.
CEO Meredith MacKenzie said one of two new vets who started with the practice in June last year works as an nutritional adviser for cattle.
"There is a lot of work out there, but we haven't been able to do it because of the shortage of vets," she said.