A decision on whether to insure you is not supposed to be based solely on the MIB report. The MIB does not have a file on everyone. But if your medical information is on file, you will want to be sure it is correct. Self-insured businesses establish a fund to cover the insurance claims of employees. Since no third party is involved, the medical records that would normally be open for inspection by an insurance company are accessible to the employer.
Most large corporations are self-insured.
Unfortunately, the laws in only a few states require employers to establish procedures to keep employee medical records confidential. After employment is offered, an employer can only ask for a medical examination if it is required of all employees holding similar jobs. If you are turned down for work based on the results of a medical examination, the employer must prove that it is physically impossible for you to do the work required. The EEOC's phone number is listed in the United States Government section in the white pages of the phone book. Your medical records may be subpoenaed for court cases.