I just was accepted to PhD programs...so I will start next fall...the first 2 years are course work and rotations so you dont start researching until your 3rd year anyway...
Options are:
Do PhD and finish in 6-7 yrs and dont decide to do MD
Do PhD then decide 3-4yrs in I'd rather be an MD and switch into an MD program and wasted those years in the PhD program
Do 1 yr of PhD, get some courses out of the way and then transfer into MD/PhD dual program so that I'm in a program preparing me for either route..some of my courses in the 1st year of PhD program might even transfer over
Right now, like i said, I like basic research but over the past 4 months I've began entertaining and inreasiningly liking the idea of possibly being an MD...I don't feel like I want to pursue it yet but I may decide I want to in a few years...I'm trying to avoid wasting those few yrs
OK. I think it's good that you've though about this. Let's discuss the possibilities more realistically...
1- how competitive of a candidate are you? How good are your grades? Have you taken the MCAT?
If not, take the MCAT now before you start the PhD. MD/PhD applications are taken in September, so you really don't have long to decide what you're going to do.
2- If you really think in 3-4 years you may reconcider the PhD... stop now. Really. the PhD is A LOT of work and VERY difficult. You will probably be contemplating killing yourself just to end the misery at that time, not just wondering if you'd made a mistake. If you have doubts now, it's not too late.
3- Assuming you're competitive and get an MCAT over 33, congratulations, you have a chance. but there is no "transfer" from PhD into MD/PhD, only the other way around. So realize you WILL be starting over. And unless you are at the same institution (very unlikely), none of your credits will transfer.
4- You don't really need to wait 3-4 years to decide you don't want to do a PhD. Most people decide just after they fail their quals.
My advice, given all you've said- is to make sure you have all courses/tests for med school completed, and that you have a realistic chance of acceptance. If you do, then apply ASAP. you should consider that it will look BAD to drop out of a PhD program. Be prepared to defend your decision. Apply for MD/PhD, and start grad school. If you're accepted, drop out of PhD, and wait for the next year to begin. If not, pretend like it never happened.