I'm on the last rotation of my third year of medical school. I'll be applying for residency in a few months and am leaning toward psychiatry, though I've considered a few other fields passively and am on cardiology right now trying to rule out internal medicine.
There was some skewed info given earlier about going to medical school not being worth it. There are a number of intangible perks that don't get mentioned, such as job security. Not the type of job security that you'll have employment, but the type where you can dictate where you want to live and still make a salary within a specific range. Comparing it to a PhD is apples and car batteries. Publish or parish is the name of the game in academia. I can't think of any other field that you get out of it exactly what you put in. What I mean by that is that in medicine, how far you go depends on you and what you invest. While this can be true to some extent in other fields, the amount of luck necessary to do well in medicine is much, much less than other fields like law or business or 90% of other fields where having a string of good luck vs. bad luck can be the difference between huge success and unemployment. There's a huge investment upfront, such as minimum 7 years post college, but it's not all bad. You may make 50k in residency, but depending on your field and program you can moonlight which typically pays $80-$100/hr. You will accrue massive amounts of debt (I've got almost 200k with a year left) but there are a lot of different angles to look at.
Chiropractic was mentioned and you'd have as much success (financially) if you were to just get a BS in business. Oh, and on that note, a bachelors in any of the sciences is pretty worthless on its own, so comparing between any life sciences degrees is splitting hairs.