As for the specifics of employment law in Illinois you would have to speak with an employment attorney in your area.  But it may not be the requirements of your employer per se.  It may actually be a requirement of the insurance company that provides the health insurance.  You should see about that.  Rates for insurance can be governed by the health of the insured although it would be illegal in most instances to deny coverage.  Also, if you challenged the issue and it came down to be decided by a Judge or someone acting in the capacity of a judge, I do not think that the request would be considered unreasonable under the circumstances.  call your state Department of Insurance and Labor.  Good luck.