On the national level, Sick day policy is determined by company standards. So unless your state has a law regulating minimum standards, sick days are a type of employment benefit designed and directed by your employer. If you call out without such benefits, it becomes an unexcused absence and depending on your company's attendance policy could lead to repercussions, including termination in an unaltered right-to-work state. Refusing to come into work on days off in such states can be considered gross insubordination, and is grounds for termination and loss of rights to unemployment.

Most companies see value in reducing turnover and retaining talent, so it is rare for their own policies to be as unforgiving as the law allows... but there are some states with practically zero employee rights guaranteed by the state.