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.

Small employer: If your employer has 1-14 employees, you are not protected under the Americans With Disabilities Act, so even if you are out sick due to a disability, you have no protection unless your state or local laws cover smaller employers. Family and Medical Leave covers employers that have 50 or more employees within a 75 mile radius of your workplace. If your employer has 1-49 employees, even if you have a serious medical condition, you may be at risk of losing your job when you come back.

Serious medical condition: If your employer has 50 or employees within a 75 mile radius of your workplace, if you've worked at least a year, and if you have worked at least 1,250 hours in the past year, you are entitled to up to 12 weeks of Family and Medical Leave for a serious medical condition. However, “serious” is pretty limited. The Department of Labor explains “serious” this way:

• any period of incapacity or treatment connected with inpatient care (i.e., an overnight stay) in a hospital, hospice or residential medical care facility; or

• a period of incapacity requiring absence of more than three calendar days from work, school, or other regular daily activities that also involves continuing treatment by (or under the supervision of) a health care provider; or

• any period of incapacity due to pregnancy, or for prenatal care; or

• any period of incapacity (or treatment therefore) due to a chronic serious health condition (e.g., asthma, diabetes, epilepsy, etc.); or

• a period of incapacity that is permanent or long-term due to a condition for which treatment may not be effective (e.g., Alzheimer's, stroke, terminal diseases, etc.); or,

• any absences to receive multiple treatments (including any period of recovery therefrom) by, or on referral by, a health care provider for a condition that likely would result in incapacity of more than three consecutive days if left untreated (e.g., chemotherapy, physical therapy, dialysis, etc.).

Disability: Assuming your employer has at least 15 employees, they're covered under the Americans With Disabilities Act. If your illness related to a covered disability, then your employer must grant a reasonable accommodation for your disability. A reasonable accommodation could include time off for a disability-related illness or treatment. EEOC explains that, “A person can show that he or she has a disability in one of three ways:

• A person may be disabled if he or she has a physical or mental condition that substantially limits a major life activity (such as walking, talking, seeing, hearing, or learning).

• A person may be disabled if he or she has a history of a disability (such as cancer that is in remission).

• A person may be disabled if he or she is believed to have a physical or mental impairment that is not transitory (lasting or expected to last six months or less) and minor (even if he or she does not have such an impairment).”