'I request to the doctor' is completely wrong, however neither expression would be said in english. you would say - I need to see a doctor I need a doctor the word 'request' in this situation would sound very strange. a similar example - 'I request a policeman' we would never say that. Rather we would say 'I'm calling the police' - when you phone for the police or doctor you are in fact requesting they assist you, but you wouldn't actually use the word request.