A pre-existing condition is any illness or injury that occurs before your policy becomes effective, including the waiting period.
Simply put, if your pet has or had any condition, whether diagnosed by your veterinarian or not, before enrolling in a pet insurance plan, it is considered pre-existing and will not be covered.
However, some companies will cover conditions like broken legs or kennel cough that heal or are curable and require no further treatment.
Here are some exmaples:
Limping Dog - Your dog has been limping for a couple of weeks so you sign up for a pet insurance policy on July 1st. You take your dog to the vet on July 3rd and he diagnoses him with a broken leg. The broken leg would be considered a pre-existing condition and would not be covered because the injury happened before you enrolled. Not Covered.
Mysterious Illness - You enroll in a pet insurance plan on December 1st and on December 20th, after your waiting period has expired, your dog stops eating. You take him to the vet and find out he has a stomach virus that requires $2,000 in treatment. Because the virus occurred after the waiting period this is not pre-existing. Covered.
Complications - Your dog was treated for a fractured hip last year and it is healed. You enroll in a pet insurance policy on March 1st and 3 months later, after your waiting period is up, your dog is diagnosed with arthritis and bursitis. The arthritis and bursitis is a result of the fractured hip and this would be considered a pre-existing condition. Depends on Company.