My understanding is that you can NOT be disciplined for following the FMCSRs. My husband got written up for taking a sick day (and no, he did NOT get any verbal warnings, just a write-up), and when he asked his boss if the write-up was in line with FMCSR rules and regs, he got the famed "deer in the headlights" stare, followed by a stammered "Uhh... I don't know anything about that." o.O
FMCSR rules clearly state that "No driver shall operate a commercial motor vehicle, and a motor carrier shall not require or permit a driver to operate a commercial motor vehicle, while the driver's ability or alertness is so impaired, or so likely to become impaired, through fatigue, illness, or any other cause, as to make it unsafe for him/her to begin or continue to operate the commercial motor vehicle. However, in a case of grave emergency where the hazard to occupants of the commercial motor vehicle or other users of the highway would be increased by compliance with this section, the driver may continue to operate the commercial motor vehicle to the nearest place at which that hazard is removed." (That's 392.3, "Ill or fatigued operator.")
I'm still trying to get a hold of a lawyer who specializes in trucking to find out if this is a violation or not. We believe it is. We're pretty sure the company broke SOME law or rule by writing my husband up, even though at the time of the write-up he was told "You don't have an attendance problem but you're still getting written up." One supervisor went so far as to tell him that he HAD to sign the write-up (incorrect) and did not give him the option of writing his own comments on the form.
As for FMLA, it does not specify that you can only use it one time for any given reason; additionally, while you do not have to show your medical records to your employer, the employer can require you to provide medical certification to justify FMLA. Generally FMLA is not a good idea for a short-term illness (such as the flu), but is designed for illnesses or other situations (such as the birth of a child or the care of an elderly parent) that will require a longer period of time away from work.