I recently posted about this subject. Yesterday, I was reading a forum post from a pet owner that had bought pet insurance and when she filed her first claim, the company requested her pet's medical records. After reviewing the medical record, the company denied the claim stating it was for a pre-existing condition. Needless to say, the pet owner wasn't very happy.
Embrace pet insurance has a Medical History Review that can give pet owners peace of mind that there won't be any surprises pertaining to pre-existing conditions when you file a claim. Other companies may be willing to do the same thing if you ask. If the company informs you that there are pre-existing conditions that won't be covered, and that is unacceptable to you, you can cancel your policy early on and sometimes receive a full refund (if the company has a e.g. 30 day money-back guarantee and you haven't filed any claims). Remember though, even if one or more conditions are excluded from coverage, there are still potentially hundreds of other conditions that will be covered under the policy. So, you'll have to decide if the pet insurance is still worthwhile to you even if there are excluded conditions.
***When I include examples from specific pet insurance companies, it is not intended to be an endorsement of those companies. I have endeavored to remain as neutral and unbiased as possible, but will from time to time point out both good and bad when I see it. My goal is always to educate pet owners about how pet insurance works and help them select the best company and policy for their pet.