An employee needs to be made aware that all absences must be accounted for. Many employers conduct informal return-to-work interviews. These need to be handled sensitively, but should be carried out. Both the employee and the person carrying out the interview should sign a form confirming that a return-to-work interview has been carried out. These forms should be kept with the employee's records and reviewed should absences become a concern to the employer.
The purpose of the return-to-work interview is to try to establish whether the absences will be recurring and if there is any reason for concern by the employer. This may depend on the employee's absence record and any emerging pattern of absence, such as "regular" Mondays taken as "sick leave" when there seems to be no genuine medical reason for this to keep occurring.