Employers are not legally "required" to know why an employee requests medical leave. However, employers may request to have a doctor's note or medical verification that the leave is necessary.
For two days off, under most but not all circumstances, employers are entitled to know but do not have to know. If the leave is part of Family and Medical Leave Act (FMLA), then the employer may not ask for the diagnosis. The medical documentation supporting FMLA need only state "a serious medical condition." If the medical leave is part of a reasonable accommodation for a disability per the ADA or Fair Employment and Housing Act, then the employer may know the diagnosis.
Yes, I know this seems like a patchwork quilt. Very few attorneys will say the law is completely rational.
twitter.com/MikaSpencer *** All legal actions have time limits, called statutes of limitation. If you miss the deadline for filing your claim, you will lose the opportunity to pursue your case. Please consult with an experienced employment attorney as soon as possible to better preserve your rights. *** Marilynn Mika Spencer provides information on Avvo as a service to the public, primarily when general information may be of assistance. Avvo is not an appropriate forum for an in-depth response or a detailed analysis. These comments are for information only and should not be considered legal advice. Legal advice must pertain to specific, detailed facts. No attorney-client relationship is created based on this information exchange. *** Marilynn Mika Spencer is licensed to practice law before all state and federal courts in California, and can appear before administrative agencies throughout the country. She is eligible to represent clients in other states on a pro hac vice basis. ***