A 6-year-old 1.86-kg (4.1-lb) spayed female Chihuahua mix was evaluated because of vomiting of 2 days' duration. When the owner arrived home on the day of the evaluation, the dog was hesitant to ambulate out of its indoor crate. The owner subsequently carried the dog outdoors where it stumbled, vomited, and collapsed. The dog had no history of medical problems and no sudden diet changes. The dog was not receiving any medications, except heartworm preventative, and had no known exposure to toxic agents or human medications; its vaccination status was current.