The disability discrimination laws limit medical and psychological examinations and disability related inquiries of employees and applicants. The limits differ depending on whether the exam or inquiry is pre-offer, post-offer or during employment.
Prior to an offer of employment all medical examinations are generally prohibited, even if they are related to the job. After an applicant is given a conditional job offer, but before he or she starts work, an employer may require medical examinations in order to determine fitness for the job in question. All entering employees in the same job classification must be subject to the same examination.
During employment, an employer may require medical examinations that it can show to be job-related and consistent with business necessity.
You can find more information in the Medical Exams and Inquiries section of the HR Library.