day 9 of fast how to tell if electrolytes are too low?

This is the first time I have fasted water only this long. I wanted to go longer because I am doing so for heart plaque and I think I need to have 14 days to have much of an improvement. I am getting weaker today have lost 10 pounds and am down to 104. I am 62 female and trying to decide if I should taper off into a juice fast to be on the safe side or if there is a way to know if I'm putting myself at risk? Thank you for any information.