Your credit score has nothing to do with the credit limit they will give you. They look at your income and your already existing lines of credit and how much of that you already used.
They will not give you a high limit to begin with because they don't know you. People with high limit cards usually had them for decades and their limit has been slowly increased over those years.
None of them are "stupid" and all of them are in business because they evaluate risk and don't hand out money to people they don't know yet.
The younger you are... the less likely you will get a high limit credit card. It just doesn't work that way.
If you need a credit card specializing in healthcare financing then try CareCredit.
Here is the link:
https://www.gogecapital.com/en/consumer-credit-financing/merchants/healthcare/carecredit/login.html