Getting FMLA leave approved can be a frustrating process, especially at a large company or governmental agency where every decision, even a relatively small one, has to be run by and approved by a number of supervisors. It’s possible that when you request medical leave, you will have to do a few trips back and forth between your doctor and your employer, where employer will request for additional information or clarification of your condition, symptoms, limitations and reasons for your anticipated leave.
In most cases, cooperating with the employer or even putting your employer directly in touch with your doctor is a good idea. You want to show that you reasonable do everything in your power to ensure that the employer is on notice of your condition and the need for FMLA.
Some employees decide to play “hardball” with their management, withholding information due to confidentiality concerns, etc… Unless you have some kind of embarrassing condition or are concerned that your management will not maintain confidentiality of your personnel records, you should disclose the required information, because the employer has the right to know the basic information about the reasons for your need for medical leave before granting that leave.