If you are sick you must inform your employer immediately and have your doctor issue you a Arbeitsunfähigkeits-Bescheinigung [statement of fitness for work]. This is a medical confirmation that you are unable to work due to illness.

More details

The Arbeitsunfähigkeits-Bescheinigung [statement of fitness for work] contains the expected duration of the incapacity to work, diagnoses and other information. The certificate itself consists of three or four parts. If you doctor's practice transmits the details on your fitness for work digitally to us, we receive the statement of fitness for work directly from the practice. Your doctor then provides you with copies for your records and for your employer.

Please note that your employer will not be able to see the diagnosis given by your doctor.