I am an EAP counselor and considering to request a copy of my client"s prescription... are there any HIPAA violations in this situation? What if he signs a consent to release information?

If you are requesting a copy of the prescription from the client's physician, they need to sign a consent form. The physician can't release the info without the patient's consent.

You would not be violating HIPAA by making the request, but the physician would, if they supplied the info without patient consent.