Our cat has been aging and two weeks ago was diagnosed with hyperthyroidism, a treatable disease and not uncommon in elderly cats. It's a problem for us because she doesn't like to be handled, although she's more tolerant of us than other people. The medication we were given to treat her is in pill form and must be given twice a day. When we first started giving it to her it wasn't hard, we crushed it and sprinkled it into her food. And that's a good thing because we could never leave her with a sitter; she would not tolerate anyone giving her a pill but us.
We took her back to the vet on the 9th for another blood test to determine if the dosage was the right amount and if it was helping. She was spot-on, the meds were perfect. Except....after that visit she quit eating. From Monday the 9th until Thursday the 12th, she ate less than a tablespoon of food. Her weight on the 9th was 3.9 lbs and on Thursday was 2.6 lbs. So, back to the vet. This time another blood test showed renal disease, also a disease of aging cats and although you can make them comfortable and add time to their lives, you cannot cure it (and it's the same disease that killed my last cat, my beloved G.R.). We were given cans of 'critical care' food, a soft pate to mix with warm water and a syringe. We were told to back off the thyroid medication; we're down to one pill a day but feeding by syringe every couple of hours. She still shows no interest in eating on her own. If we can reach that point, there is an appetite stimulant we can add to her food. In our attempt to entice her to eat we purchased every brand of canned food that was on the market. We have at least 50 cans of cat food in 'her' cabinet. In the end, we throw away everything that's been opened and we're continuing with the critical care diet. If we can get her eating on her own again, there will be a special diet for cats with kidney disease and I understand from reading on line that many cats don't like it. But we will deal with that when we get there. In the meantime, she drinks copious amounts of water, will not allow an IV which would help her dehydration, and sleeps around the clock. We wake her up to feed her, we clean her up (this is a really messy process), let her drink some water and put her back in her bed.