To be eligible for a disability retirement annuity under  FERS or  CSRS, you must be able to show that:

1) Eligibility. You completed at least 18 months of creditable service in a position subject to FERS, or five years of creditable service in a position under the CSRS,>

2) Disability.You became disabled because of a medical condition, resulting in a service deficiency in performance, conduct, or attendance (if there is no such actual service deficiency, the disabling medical condition is incompatible with either useful and efficient service or retention [...]

The short answer to that question is “generally, yes”.

Disability retirement is available to Federal Employees who become disabled in the course of their employment. The disability need not have occurred while at work.  Whether or not an employee is eligible for  disability retirement depends on which Retirement System the employee works under.

CSRS employees must be employed for a minimum of 5 years and be no longer able to effetcively perform at their current grade or pay level due to a [...]