Under the federal Family and Medical Leave Act (FMLA), covered employees have the right to substitute sick days for any part of a leave taken because of their own serious health condition or to care for a spouse, child, or parent. The Act does not supersede state laws if they provide greater leave rights to employees. Employers that provide sick leave and are covered by both state law and the federal FMLA should carefully review the various provisions of both laws to make sure that employees receive the more liberal leave benefits.
Furthermore, under the federal Americans with Disabilities Act, permitting the use of accrued paid leave or unpaid leave is a form of reasonable accommodation when necessitated by an employee's disability. An employer must allow the individual to use any accrued paid leave first. If that is insufficient to cover the entire period, the employer should grant unpaid leave. There is additional information.