850 is the best FICO score anyone can get. CareCredit refused to lower their interest rate from 26.9%. Said it is the interest rate "across the board" for all. I do know that if your medical person applies, the rate will be whatever he/she and CareCredit agree on which can be lower. But if you have them as a credit card they will charge 26.9 percent interest no matter how perfect your credit is. About that promotional rate for $200 or more expenditure: I paid $204 for my mother's medicine using CareCredit. They said that since i used the card at a pharmacy, the promotional rate did not apply and I couldn't have it.
If your medical person or vet applies for you you may end up with a good deal. Never apply for it yourself. But beware, once that interest free period ends, you are in for it, as others here have explained.
Apply for a Visa or MasterCard with a good long interest-free period after first opening the account, and get your procedure done (or your pet's) and then pay as you normally would. And watch out for any card that says if you don't pay it off by the end of the promotional period, they will charge you for all the back interest that you didn't have to pay.