In addition to all the science classes you have to take across disciplines (Bio I & II, General Chemistry I & II, Physics I & II, Organic Chemistry I & II, Bio Lab I & II, General Chemistry I & II, Physics Lab I & II, Organic Chemistry I & II - where in some instances the highest scores in tests are 60s always graded on a curve). These are just the pre-requisites for the first two years of undergrad in addition to taking the university pre-requisites just to graduate with a Bachelor's. In addition to that, you have to take other science electives the remaining two years of under-grad. In addition, you have to do research work or shadow a physician during your summers in order to bolster your application for Med school.
Wait it's not done yet, you have to take the MCATs (Medical school entrance exam) after you have gotten a good score then you go on interviews at the school. Mind you admissions to medical school has its politics and it costs. State universities with medical school tend to prefer students who are either residents of the state or can prove they have some ties to the state because they don't want to educate someone on taxpayers dime and then have him/her leave the state to practice medicine in another state. Some state schools actually will accept a state resident with lower academic credentials than an out of state applicant. An out of state applicant has to be exceptional damn near perfect GPA, MCAT score and good research background. Admissions rate are single digits for most med schools.
The application process will cost you about $2000 minus Kaplan prep courses (which everybody takes no matter how brilliant they are). Then you get to med school, board exams. But I will leave it at that. I believe that you can get your target intended job for engineering after undergrad while in medicine you have to go through the gauntlet of med school in addition to residency.
Medicine for the win.