29 C.F.R. § 825.115

A serious health condition involving continuing treatment by a health care provider includes any one or more of the following:

(a) Incapacity and treatment. 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:

(1) Treatment two or more times, within 30 days of the first day of incapacity, unless extenuating circumstances exist, by a health care provider, by a nurse under direct supervision of a health care provider, or by a provider of health care services (e.g., physical therapist) under orders of, or on referral by, a health care provider; or

(2) Treatment by a health care provider on at least one occasion, which results in a regimen of continuing treatment under the supervision of the health care provider.

(3) The requirement in paragraphs (a)(1) and (2) of this section for treatment by a health care provider means an in-person visit to a health care provider. The first (or only) in-person treatment visit must take place within seven days of the first day of incapacity.

(4) Whether additional treatment visits or a regimen of continuing treatment is necessary within the 30-day period shall be determined by the health care provider.

(5) The term extenuating circumstances in paragraph (a)(1) of this section means circumstances beyond the employee's control that prevent the follow-up visit from occurring as planned by the health care provider. Whether a given set of circumstances are extenuating depends on the facts. For example, extenuating circumstances exist if a health care provider determines that a second in-person visit is needed within the 30-day period, but the health care provider does not have any available appointments during that time period.

(b) Pregnancy or prenatal care. Any period of incapacity due to pregnancy, or for prenatal care. See also § 825.120.

(c) Chronic conditions. Any period of incapacity or treatment for such incapacity due to a chronic serious health condition. A chronic serious health condition is one which:

(1) Requires periodic visits (defined as at least twice a year) for treatment by a health care provider, or by a nurse under direct supervision of a health care provider;

(2) Continues over an extended period of time (including recurring episodes of a single underlying condition); and

(3) May cause episodic rather than a continuing period of incapacity (e.g., asthma, diabetes, epilepsy, etc.).

(d) Permanent or long-term conditions. A period of incapacity which is permanent or long-term due to a condition for which treatment may not be effective. The employee or family member must be under the continuing supervision of, but need not be receiving active treatment by, a health care provider. Examples include Alzheimer's, a severe stroke, or the terminal stages of a disease.

(e) Conditions requiring multiple treatments. Any period of absence to receive multiple treatments (including any period of recovery therefrom) by a health care provider or by a provider of health care services under orders of, or on referral by, a health care provider, for:

(1) Restorative surgery after an accident or other injury; or

(2) A condition that would likely result in a period of incapacity of more than three consecutive, full calendar days in the absence of medical intervention or treatment, such as cancer (chemotherapy, radiation, etc.), severe arthritis (physical therapy), or kidney disease (dialysis).

(f) Absences attributable to incapacity under paragraph (b) or (c) of this section qualify for FMLA leave even though the employee or the covered family member does not receive treatment from a health care provider during the absence, and even if the absence does not last more than three consecutive, full calendar days. For example, an employee with asthma may be unable to report for work due to the onset of an asthma attack or because the employee's health care provider has advised the employee to stay home when the pollen count exceeds a certain level. An employee who is pregnant may be unable to report to work because of severe morning sickness.