I may apply to medical school as early as next year, but I would like to know what effect a 250k-300k federal loan package (mostly unsubsidized) would have on my current credit score (oldest revolving account~ 3yrs). Will the effects be immediate as I take out the loans and will my credit score drop dramatically (due to the high debt-to-limit ratio) after I graduate from medica school and have to start paying them back?
Also, will these medical school loans affect my current credit card accounts/limits? future auto/mortgage loan approval-chances/rates?
Initially, you'll see a small drop in your score from any hard inquiries, for each new account, and also because your Average Age of Accounts will drop. How much drop you'll see will depend on how many new loan accounts are opened, your current AAoA, and when they are opened. Overall though, it shouldn't be a massive change. Installment loan utilization has very little impact on your score.
Your debt-to-income ratio has no impact on your credit score, but it can substantially impact your ability to get credit. Most applications for credit (especially car and home loans) will ask for your income and other debt obligations and factor that information into how much they are willing to lend you. I doubt that any current credit accounts would reduce your limits just because you took out student loans, but you may see future CCs not offer as high of a limit until you establish an income that shows you can comfortably pay off those loans.
I have substantial loans from attending professional school (vet not MD) and I honestly don't think it impacted my score that negatively from what I remember. Just make sure that you don't start using CCs too much in med school. Sometimes it's hard to make ends meet when you're living on loans but you just have to keep yourself to a budget and use your CCs wisely (i.e. emergencies).
My current student loans have not negatively impacted my credit score. My SL are double my income at current and I'll be starting grad school in the spring. I was approved for a used car in March for a decent rate as well, at least for me and my credit.