Can my employer force me to work overtime?
Technically, no one can force you to work. That would be slavery and is prohibited by the U.S. Constitution. However, your employer is generally correct. They may order you to work overtime and discipline or terminate you from your job if you do not work the extra hours. There is no law that prohibits them from doing this (for the most part). However –
If your employment is governed by a labor contract, your contract or collective bargaining agreement may include a provision that changes the answer to this question. Unions, for example, may negotiate different rules in the contracts between the employers and their workers.
There is one specific area where the above advice on mandatory overtime is incorrect. According to Act 102, health care facilities may not require employees to work more than agreed to, predetermined, and regularly scheduled work shifts unless there are emergent circumstances (specified by the law). The law went into effect on July 1, 2009 and applies to individuals in direct patient care or clinical care services who receive an hourly wage or are classified as nonsupervisory employees for collective bargaining purposes. Health care facilities are defined to include, among certain other places, hospitals, hospice, ambulatory surgical facilities, long term care nursing facilities, and cancer treatment centers using radiation therapy on an ambulatory basis. It does not cover an office used primarily for the private or group practice of a health care practitioner. There are lots of exceptions and carve outs to the coverage of this law (physicians, physician assistants and dentists are not covered, for example).