Liz Buchanan BVSc MRCVS
Hello. It sounds as though your veterinary team have assessed the urine and found crystals, so they should have reccommended steps to prevent crystals recurring. Depending on the system your team has in place, the receptionist might have details of this on your notes. If this hasn't yet happened, we would reccommend booking an appointment with your veterinary nursing team in order that you can follow their advice. S/d is usually a prescription diet, so it does have to be prescribed for the patient by their team.