The quick answer is that you first do a residency (in your stated case) in EM or in Prev. Med, or Peds. After that you enter a two year ACGME accredited (if you are interested in board certified medical toxicology) or a one year self designed (and non-accredited) toxicology fellowship. Of late there have been decent fellowships that have gone unfilled, but don't let that lull you into a sense that they are easy to get into. Most would rather be unfilled than filled what they might consider less qualified applicants. The "boards" for toxicology are arguably among the most difficult in medicine and must be passed on the first or second attempt. In short, it is a long road for little pay increase, but if you've got the "Mr. Yuk" bug, like Southerndoc and I, it is sooo cool.
- H