Ok, back the train up here. The OP is not asking whether or not s/he should do this whole med school thing but whether s/he should go for the 2nd bachelor's or the post-bacc, so the "you're screwed" sentiments are not cool . . . particularly as this is his/her first post. (Welcome! and way to go, by the way!
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My advice is something I wish someone would have told me when I first thought "well, that didn't work, how about med school!" I dove headfirst into the classes, but not the lifestyle. EXTRACURRICULARS ARE RIDICULOUSLY IMPORTANT. Your grades are not going to set you apart and might cause you to be screened out at some schools, but for the others, you MUST have something on that application that says "This person is extraordinary. This person WANTS this." Volunteer . . . a lot . . . for a cause or a place (or a few!) that shows your humility, compassion, and desire to truly "help people" (e.g. free clinic in underserved area). Everyone who applies to medical school wants to help people - you won't ever need to vocalize this if you can show it through the time you put in AND the initiative you take. That's key as well - don't just put in your time - be a leader. Maybe organize something: a blood drive, a charity event, etc. You went to business school . . . that could be a huge asset in this area! And shadow a doctor . . . or a few over a decent amount of time. It's essential to understand what it's actually like "in the trenches." Maybe seek out some sort of immersion experience - like going to a third world country to aid in delivering health care services. Or seek out a research experience (maybe the second bachelor's would provide you with that experience.) Also, befriend your profs! Talk to them, ask questions, be an engaged student. My intro bio prof had told all of us from the get-go that if there was something we were interested in to talk to him about it - he would be happy to mentor any post-bacc in a research project. Why didn't I do that? I don't know, but I certainly wish I had.
In sum, BE PROACTIVE. A few substantive experiences are key (don't try to do all of the above, though - padding the resume is transparent). Also, if there is something you love to do now (run, play an instrument, etc.) don't give that up because you're too busy. Adcomms like to see that you have sustained interests outside of the medical realm (or so I am told). (Sidebar: I really wish I hadn't dropped the clarinet like a bad habit after college graduation . . . I should have joined a community band. it would have been fun, and I could have demonstrated that i have a life outside of class, other than watching copious amounts of TV with my husband.

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Anyway, all of these experiences will:
(a) strengthen your desire to practice medicine (or make you realize you've made a mistake - which would ok too - better than realizing this as an M1, 2,3, or 4)
(b) help you develop close relationships with mentor-type people, who could then truly speak to your abilities, character, tenacity, generosity, etc - in other words, they can "testify" to the adcomms that you have what it takes. Letters of recommendation are an area where you could shine.
Yes, you need to get amazing grades in whichever you choose to do - post-bacc or second bachelor's. But you also need to think outside of the "grades and test scores are everything" box. I didn't, and I can't stop kicking myself now that I'm applying and I have no solid evidence on my application that I'm really interested in being a doctor.
🙁
Finally, whenever you're ready to apply, apply early (it's practically the SDN motto, so you'll see that on here a lot.
👍) That's another reason I'm kicking myself now! But, the eternal optimist, I know it will work out for me eventually, and you have to believe that as well.
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Good luck!!!

(and sorry to everyone for the long post
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