No. An employer is not entitled to your diagnosis. However, it is entitled to enough information to assess your request and identify a reasonable accommodation.  

You only need to provide information about your functional limitations and restrictions, and how your condition affects your ability to perform your job. It is your responsibility to ensure your employer receives this information from your health care provider in a form that is relevant to your job requirements.  

It is helpful to share your job description with your health care provider so they understand the nature of your work and can clearly identify your limitations. Your health care provider should also indicate how long those limitations are expected to last. This information helps the employer determine the appropriate accommodation and its expected duration.