The Spanish words doctor/doctora and médico mean one and the same profession though are used in different contexts.
The words doctor (masculine) and doctora (feminine) mean a certain doctor, for example:
El doctor Jiménez es cardiólogo y la doctora Rodríguez es pediatra – Doctor Jiménez is a cardiologist, and doctor Rodriguez is a pediatrician
Therefore, it would be correct to say
CORRECTO: Me va a operar la doctora Blanco – Doctor Blanco is going to operate on me
INCORRECTO: Me va a operar la *médicoBlanco
Speaking to a specific doctor, the words doctor/doctora are used:
CORRECTO: Buenos días, doctor. Gracias, doctora – Hello, doctor. Thank you, doctor
INCORRECTO: Buenos días, *médico. Gracias, *médico
On the contrary, the word médico usually refers to doctors in general:
CORRECTO: Mañana voy al médico. Mañana tengo médico a las 9 – Tomorrow I’m going to the doctor’s. I have an appointment with the doctor at nine tomorrow
INCORRECTO: Mañana voy al *doctor. Mañana tengo *doctora las 9
The word collocation "attending physician" or "general practitioner " is translated into Spanish as "médico de cabecera" or "médico de familia". This word is also usually used to refer to a profession:
SUENA BIEN: Mi mujer es médico – My wife is a doctor
NO SUENA BIEN: Mi mujer es *doctora
In English-speaking countries, Doctor usually refers to specialists in any field. In Spain, doctor/doctora does not refer to people who are not related to healthcare:
(inglés) Dr. Jetkins = (español) Señor Jetkins