Medical confidentiality is a fundamental prerequisite in the patient-physician relationship based on trust and goes back to the Hippocratic oath. It is clearly defined in the German Constitution as well as the medical professional code of conduct. A breach of confidentiality can result in criminal sanctions and professional consequences as well as civil claims for damages and compensation by the affected patients. In routine clinical practice situations repeatedly occur which lead to uncertainty regarding the limits of confidentiality, the right to silence and the obligation to disclosure. The purpose of this article is to explain the legal foundations of medical confidentiality, the right to silence and the obligation to disclosure and to provide practical support for critical questions in routine clinical practice.