An employee with a disability who has been granted medical leave under the ADA may return to the same job unless the employer demonstrates that holding the job open would cause undue hardship to the business or organization. If an employer has the reasonable belief that an employee will be unable to continue performing essential job functions, or will pose a significant risk to the health or safety of their self or other employees due to a medical condition, the employer may make disability-related inquiries or require the employee to have a medical examination. Any inquiry or examination must be limited to what is needed to assess the employee's ability to work. The employer may not use the employee's leave as a justification for making unrelated inquiries or requiring an unrelated medical examination.
An employee may have also been granted medical leave under the Family Medical Leave Act (FMLA). In this case, an employee has a right to return to the same or similar job after his/her leave has expired. The FMLA allows employers to require a return-to-work certification from a health provider for all medical leaves, as long as the same requirement is applied to all employees with similar job positions who are returning from leave, not just those on FMLA leave.
The FMLA and the ADA both require a covered employer to grant medical leave to an employee in certain circumstances. For more information go to: http://www.eeoc.gov/policy/docs/fmlaada.html.
For additional information, take a look at the following resources:
FAQ: What is considered an “undue hardship” for a reasonable accommodation?
Fact Sheet: Work-leave, the ADA, and the FMLA