Mmm that is low. The electrolytes are just checked on a normal blood draw - our vet checks potassium and sodium. We sometimes also get liver values checked as well. Here in NZ it only costs about $20-30 to get the electrolytes checked. When we think that something is slightly amiss I request the vet to take more blood on the first draw, they courier it with the other vials and it's at the lab as a back up if we want further tests done.
I have a rather large folder with all of Sabre's tests and always get copies of the results. I keep these not only for my reference but just in case he crashes when on holiday or we have to go to an emergency vet who is not familar with his case so all the information is on hand.