No American labor laws directly address the issue of 12-hour work shifts, but related laws apply, states the Houston Chronicle. There is no limit on work hours, but employees must receive overtime pay after 40 hours in one work week, and some states mandate overtime pay after eight hours' work.
The U.S. Fair Labor Standards Act states that the employee doesn't require extra pay specifically for weekend or night work, according to the U.S. Department of Labor. However, the FLSA does mandate pay for non-exempt workers of not less than one and a half times their regular rate for the time they work beyond 40 hours in a single work week. In some states, such as California, hourly employees who work beyond eight hours in a workday are entitled to twice their hourly rate for any hours worked beyond 12 in one day, states the Houston Chronicle Guide to Business and Workplace Relations.
Although the U.S. Fair Labor Standards Act doesn't require that employers provide breaks or meal periods to workers, some states may have requirements for breaks or meal periods, states the U.S. Department of Labor. As 12-hour shifts leave employees with only 12 additional hours in the day for meals, sleep, recreation and other life responsibilities, it's best for 12-hour shift workers to have lunch and rest breaks at work as well as scheduled days off between workdays, states the Houston Chronicle.