While you can be held in contempt for refusing to provide documents or testimony in response to a grand jury subpoena, you are under no obligation to talk to prosecutors outside of the presence of the grand jury. Although it is common for prosecutors to seek information informally (although a request may seem formal to someone not familiar with the judicial process), these informal requests for information can and generally should be denied. As a general rule, physicians, executives, personnel, and other individuals should not speak with federal prosecutors in the absence of their attorneys, and you are well within your rights to demand legal representation at any time outside of the courtroom.