A 10 year old male castrated mixed breed dog presented to Cornell University Hospital for Animals for hypocalcemia and a 3 day history of muscle fasciculations, ptyalism, and inappetence. Upon presentation, the dog’s ionized calcium was 0.8mmol/L. He was stabilized on calcium gluconate, calcium carbonate, and Plasmalyte A. Bloodwork revealed a hypocalcemia, hyperphosphatemia, and hypomagnesemia. Abdominal and cervical ultrasound revealed no significant findings. In lieu of any kidney abnormalities, his hypocalcemia was diagnosed as presumptive primary hypoparathyroidism. Calcium supplementation was discontinued in order to obtain a hypocalcemic blood sample for a parathyroid hormone (PTH) and ionized calcium (iCa). He was then stabilized and discharged into the care of his owners on calcitriol and calcium carbonate. The PTH/iCa panel demonstrated an inappropriately low PTH in the face of hypocalcemia, giving a definitive diagnosis of primary hypoparathyroidism.