You doubt the accuracy of a medical certificate?
In this case, as an employer, you have several possibilities to review the matter.
The answer in detail
An employee reports sick and supplies evidence by way of a medical certificate. You, the employer, doubt the accuracy of the certificate. In such a case, you as employer can approach an independent medical examiner to review the matter and get a second opinion. This is permitted in law. In addition, we recommend that you include this legal right in your employee contracts. Here you'll find a sample agreement.
Vorlage Aufgebot zur vertrauensärztlichen Untersuchung