People are sometimes surprised to learn that, generally speaking, it's legal for an employer to fire an employee because the employee misses work because of an illness or medical condition if the Family and Medical Leave Act (FMLA) doesn't apply for some reason. That can be true even if the employee has a medical excuse or doctor's note for missing work. It can even happen if the employee was eligible to seek FMLA protection for the absence.
There are several ways that the FMLA may not protect an employee's medical leave. The employer may not have enough employees to be covered by the FMLA. Or the employee may not have worked for the employer long enough or for enough hours to qualify for FMLA coverage. Those are the two most common reasons why a medical absence may not receive FMLA protection. Absent FMLA protection, it's often legal for an employer to fire an employee for missing work because of injury, illness, or some other medical condition.
Of course, even if the employer's covered under the FMLA and the employee's otherwise eligible for FMLA protection, the employer may still deny FMLA time and fire the employee for missing work. That could happen if the employee's exhausted all FMLA entitlements (480 hours per 12-month period, as determined by the employer). But FMLA denial could also happen of the employee's medical issue is not severe enough to receive FMLA protection.
Limiting our discussion solely to an employee's own condition, and not that of a family member, the FMLA only applies when the employee has a "serious health condition." That's not always an issue, but the situation can be tricky for lesser illnesses that don't cause hospitalization, extended incapacity, etc. because such conditions don't always qualify for FMLA protection. Employees need to be careful in such situations and not assume that they have FMLA protection simply because they're sick, even if they miss some work and have a medical excuse or doctor's note. As noted above, normally an employer can legally fire an employee for absences caused by a medical condition if for any reason the employee doesn't have FMLA protection.
The United States Department of Labor's FMLA regulations, which courts generally follow, state that "[o]rdinarily, unless complications arise, the common cold, the flu, ear aches, upset stomach, minor ulcers, headaches other than migraine, routine dental or orthodontia problems, periodontal diseases, etc. are examples of conditions that do not meet the definition of a serious health condition and do not qualify for FMLA leave." You'll note that the Department of Labor leaves open the possibility that severe instances of such medical conditions could result in FMLA protection if the medical condition meets the definition of a "serious health condition." That means that the medical condition must have caused either inpatient medical care or "continuing treatment" by a healthcare provider.
"Continuing treatment" means a period of incapacity of more than three consecutive, full calendar days, and any subsequent treatment or period of incapacity relating to the same condition that also involves either treatment by a health care provider two or more times within thirty days of the first day of incapacity (unless extenuating circumstances exist) or treatment by a health care provider on at least one occasion that results in a regimen of continuing treatment under the supervision of the healthcare provider, such as prescription medication. 29 C.F.R. § 825.115.
For "continuing treatment," the first (or only) in-person treatment visit must take place within seven days of the first day of incapacity. Covered treatment includes examinations to determine if a serious health condition exists and evaluations of the condition, but does not include routine physical examinations. It also does not include a phone call to discuss the situation with a health care provider; the employee must be actually seen and examined by the medical provider. The Department of Labor's FMLA rules also clarify that a "regimen of continuing treatment" after a single visit to a medical provider does not include taking of over-the-counter medications such as aspirin or antihistamines, or bed rest, drinking fluids, and other similar activities that can be initiated without a visit to a health care provider.