11 Year old female american shorthair, vaccinated while young (not sure against what)

For the last few days she's been acting lethargic, moving slowly, drinking excessively and eating strange foods (Salty stuff, mostly) and she has lost weight.
My mother and I plan on taking her to the vet this weekend, we think its feline diabetes, but of course we cannot be sure until then. Is there anything I can do until then?

Please help

thank you