You're speaking with Dr. Michael Salkin. Welcome to JustAnswer. I'm currently typing up my reply. Please be patient. This may take a few minutes.
I'm sorry that your question wasn't answered in a timely manner especially because you're described a critically ill Pepsi who needs the attention of a vet at your earliest convenience. An anorexic and lifeless 14 year old will need hospitalized intensive supportive care. Degenerative disorders such as chronic renal and hepatic failure as well as age-related malignancies should be important differentials in such a patient.
I regret that my state board of veterinary examiners doesn't allow me to speak to customers by phone in this venue but other experts in this category may be able to assist you in this regard. Please let me know if you'd like another expert to do so and I'll opt out of this conversation. Please stay in the conversation if you wish.