In German letters and e-mails, the salutation includes the academic title. Sehr geehrte Frau Dr. Freudenreich. Sehr geehrter Herr Professor Knodel. A person with several titles is addressed by the highest one only. In the address field, all titles appear, as in Professor Dr. Dr. Karl Meier. A guide for students at the University of Trier notes that many a chief physician would not accept it, even from a patient, if he were called only Herr Doktor instead of Herr Professor. It also notes that colleagues inside academia usually drop titles among themselves.
In everyday speech, the title has merged with one profession. Zum Doktor gehen, to go to the doctor, means to see a physician. In a hospital, a white coat is often enough to be called Herr Doktor or Frau Doktor.