Can my employer require me to use my accrued sick or vacation leave to cover part or all of my FMLA leave?

Yes; generally, an employer may require an employee to use of their accrued paid leave, whether it be sick leave or vacation leave, to cover some or all of their FMLA leave.  The employee may choose to cover some of their FMLA leave time with accrued paid leave. This issue should be covered when FMLA leave is initially approved and discussed.