If the employee submits a complete and sufficient certification, the employer may not request additional information from the health care provider. The employer may, however, contact the health care provider for authentication and clarification of the certification after the employer has given the employee an opportunity to cure any deficiencies in the certification. To make this contact, the employer must use a health care provider, human resources professional, leave administrator, or management official. Under no circumstances may the employee’s direct supervisor contact the employee’s health care provider.
Authentication means verification that the certification form was completed or authorized by the health care provider. Clarification means contacting the health care provider to understand the handwriting or the meaning of a response. Employers may not ask health care providers for more information that is contained on the form.
 29 C.F.R. § 825.307.