yes the low potassium can be because of diuretics especially lasix
now you have not told me your age and whether you have any other ailment like high BP
as altered renal function goes with that with due course of time.and with increasing age too there is a little rise in s.creatinine
as the GFR decreases.
plus are you taking any other drugs as renal impairment is common side effect of a no of drugs.