Actually, the only real legal issue the company can use is reliability. Whether they are self insured or contract through an insurance company, they can't "slap" yu for using the health insurance. However, if you or a family member has a chronic illness, and you do not show up for work because of that, then you do have reliability and dependability issues. Here is the rub, I am not sure that the employer / supervisor giving you the review can say much more than something about reliability or dependibility but, they do not have to keep you employed either! Be sure you cover all your bases, if it is a family member, make sure that you use vacation time when necessary and don't forget FMLA.

Good Luck