Docteur and Médecin

Strictly speaking, docteur means the academic degree and médecin the profession of a medical doctor. However, docteur is often used in place of médecin -- just as in English.

Médecin is the same for both genders. That's just the way it is, no specific reason. Docteur is, traditionally, also the same for both genders. Recently, that seems to be a bit more fluid with doctoresse used as the female form, but I don't hear it used frequently.

Possibly to clarify the answer above, if you are are addressing an actual licensed physician, you would address them as Docteur (last name) or simply Docteur as in “Merci Docteur” You can use the two words interchangeably as in “ Je vais chez le docteur “ or “ Je vais chez le médecin “ Although you’d probably hear the second more often. If you were speaking to a friend about a recent doctor’s visit, more often the doctor or clinician would be referred to as your médecin; for example: “J’ai vu mon médecin hier matin” instead of “J’ai vu mon docteur hier matin “ Although both would be perfectly acceptable. Docteur is used more when addressing the actual physician just like we do in English. Médecin encompasses the doctor, the physician assistant, the nurse practitioner, the practitioner, clinician, etc. There are feminine derivatives for both Doctreuse and Mèdecine”, but usually the masculine forms are considered acceptable for both words and are more commonly used.