It takes about 11 years to become a doctor, in which first 4 years are for college, next 4 in medical school and last 3 for house job/ training. This doesn’t include post graduation specialization, which might take as long as 8 more years. For more details visit http://www.bls.gov/k12/help06.htm
It takes 4 years to finish undergraduate schooling, this may either be medical related or not. It takes another 4 years to finish medical schooling, this will be your general practicing. If you want to become a specialist on a particular field you have to go through another few years in college.