I think by some of the comments that you made in the end of your post that there are other issues besides the hypoglycemia. I am surprised that no one brought up ADA. Like HIPAA is is greatly misunderstood. It says that you have to make a reasonable accommodation, but in the end, they must still do the job. The fact that you allow them to have food and time to treat his blood sugar should be compliance. I believe if I were in your shoes I would start the documentation trail with the lack of compliance of the Chief's request. Use progressive discipline and if non compliant and you send them home, you may be able to use your attendance policy here too. If necessary, you may be able to supply your documentations and concerns to a physician of your choosing and require that employee to have a fitness for duty evaluation done. Of course if you require them to go to your physician, you will have to pay for it. If they are not deemed fit for duty, or progressive discipline takes effect, you can remove the employee from the roster. It is reasonable to question division making and ability to drive your vehicles with frequent episodes of altered mental status in the face of non compliance.