Depends on 2 things.
1. Is your CoA for the medical school you are accepted to (or are applying to) below the stafford loan cap of ~$40,000?
If so, then credit doesn't matter, you're good.
2. If your CoA is above the stafford loan cap of ~40k, then you will need a PLUS loan to pay the rest. There is a
basic credit check: Borrower cannot be 90 days or more delinquent on the repayment of any debt or the subject of a default determination, bankruptcy discharge, foreclosure, repossession, tax lien, wage garnishment or write-off of a Title IV debt during the last five years.
It does not matter what your credit score is for either loan.