The general rule is that an employer may require recertification of a serious health condition no more frequently than the duration of the prior certification or every 30 days, whichever period is longer. For example, if an employee begins leave for a serious health condition with a certification that states that leave is necessary for 40 days, the employer may not seek recertification until the 40 days have passed. However, regardless of the duration of the original certification, the employer may require recertification every six months in connection with an absence.

There are several exceptions that allow an employer to obtain recertification more frequently than every 30 days. More frequent recertification may be required if:

1.The employee requests an extension of the leave.

2.The circumstances described by the previous certification have changed significantly. The regulations refer to changes in the duration or frequency of absences or the nature or severity of the illness. For example, a medical certification stated that an employee would need leave for one or two days periodically when the employee had a migraine headache but the employee's absences for migraines tend to last for four or more days. Another example might be a suspicious pattern of the employee's taking unscheduled FMLA intermittent leave adjacent to scheduled days off. Either of these cases might constitute changed circumstances that would allow a recertification in less than 30 days.

3.The employer receives information that casts doubt upon the employee's stated reason for the absence or the continuing validity of the certification. The regulations offer the example of an employee who obtains FMLA leave for four weeks due to knee surgery but then is discovered playing in the company softball league during the third week of leave.

Source http://www.faegre.com/9744