I don't think there is anything intrinsic about it that will put you at a disadvantage. Perhaps people will want to know why you changed your mind, since when you applied to medical school you had already finished your PhD. This is not much different from wondering why you want to do a joint program though. I think as long as your explanations are adequate, you're ok. It also can be a disadvantage trying to go back and study for the MCAT, take any prerequisites you didn't have, etc. Overall, I think it is an obstacle that can be overcome but you really need to want to do it.
The biggest disadvantage is that most PhDs-to-MDs have to pay for med school. I was very fortunate to get a scholarship, but this is the exception, not the rule.
OP, once you finish med school, there is no inherent difference between MD/PhD grads and PhD-to-MD grads. But if you're a premed and you think you want both degrees, my advice as a PhD-to-MD is that you should apply to combined programs. If your stats are not competitive enough to apply to combined programs, then you should apply to MD-only programs, because it's much easier to get into grad school than it is to get into med school. Get yourself into med school, and you can get the PhD during med school or do a research fellowship after you graduate.
Edit: Ok, looking through your post history, I see you are already a PhD, and that you are from FL. (So am I.
🙂) In that case, I recommend that you contact REL Larkin, who is the admissions director at UCF. He can give you some excellent app counseling. Just call their admissions office and ask for an appointment with him.
On a more general note, being from FL is a huge boon. We have a lot of state schools, and they all protect their seats for state residents, even Miami. If you can get 30+ on the real MCAT, you will have a very good chance of getting into several of our state MD schools. Other considerations: if you haven't yet started getting some clinical experience (shadowing, volunteering in a medical setting), you need to start, yesterday. This is an *essential* EC, and the FL schools are big on service and clinical activities. Also, you will need to start thinking about whom you will ask for LORs. Finally, go to the Nontrad forum, and look through our FAQs. You will find a lot of info that we have compiled in there that will help explain the process and answer questions specific for older applicants. Start with
this list. But most importantly, call REL. Seriously.
Hope this helps, and best of luck.
🙂