Donna Ballman, an employment law blogger, offers the following on what employees need to know about their legal rights if they have to call in sick:

Minor illness: If you're out sick for a day or two with, say, a cold or something minor, you have little legal protection under federal law. The laws that protect you for illness only protect you if you have a serious medical condition or an illness relating to a disability. Doctor's note or no, if you live anywhere but Montana you're in an at-will state, meaning you can be fired for any reason or no reason at all. That includes being sick (unless your state or city has a paid sick leave law).

Safety violation: OSHA is the federal agency that covers safety violations. If your illness makes it unsafe to work, then you may be protected if you refuse to break the law. In a recent case, a trucker taking narcotics for an illness who refused to drive in violation of trucking safety laws was reinstated to his job. If you work in the health industry or food service, if you are contagious, or if you are in a regulated industry, work safety laws may require that you not go to work sick. Most people, however, are not covered.