I have two cats, both of whom are pretty old.
Our old girl
The older cat is 17 years old (sometime this month, as she was a ‘barn cat’ we don’t really know her exact date of birth). She started off as a cat that my roommate and I out of college thought would be good. The roommate left after a couple of years, and the cat stayed with me. She was never sick a day in her life, but a checkup a couple of years ago revealed that her kidneys were starting to fail. This is pretty common for older cats.
The vet also discovered a slight heart murmer.
The vet advised that I start treating her by injecting fluid under her skin. This would allow more liquids to flow through her kidneys, more than she could get by drinking water. The vet advised that each bag, which would last roughly a week, would cost $28. I found an alternate source that costs $10 per week, and the vet agreed to write a prescription to allow me to purchase the medication.