The common usage of doctor is to refer to a medical professional. Doctors may be human medical doctors (M.D.) or animal doctors (Veterinarian, D.V.M.). Doctors concern is to prevent disease and injury and to restore health. The science of medicine involves an understanding of anatomy, physiology, chemistry, and technology.

1. In high school, you'll need to have excellent grades, with a focus in biology, chemistry, mathematics, and computer classes.
2. Get a Bachelor of Science degree in biology, chemistry, or psychology, or minor in one of those subjects. You'll need to have a GPA of at least 3.5 to be competitive.
3. For a human doctor, take the MCAT and score well. You'll need to get 11-12s on the physical sciences, biological sciences, and verbal reasoning sections (33-36 cumulative score) and do well on the writing essays to get into top schools like Duke, Harvard, Stanford, or Johns Hopkins.
4. For an animal doctor, there is no special test in the U.S., and you'll need to take the standard GRE. Many veterinarian schools are extremely competitive, and you'll need to score at least 1400 in the GRE.
5. Apply to, be accepted, and complete human medical or vet medicine school.