Do I ever have to pay back the medical bills that were paid by my own insurance company or my employer's health plan?

Believe it or not, the answer is sometimes "yes". There is a federal law called ERISA (the Employee Retirement Income Security Act of 1974) that may require you to reimburse your own insurance company or your employer's health plan using any money that you recover in your personal injury case. It is also important that you review with your attorney the terms of your own insurance policy to see if you're required to repay any of these costs.