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Hello there, this is Dr. Jess. I am sorry to hear about Red. Any time I see an older kitty who is having rapid weight loss I worry about a few different diseases, including Diabetes, Hyperthyroidism, Kidney disease, and Inflammatory Bowel Disease, and unfortunately, cancer. It is impossible to diagnose any of these without doing bloodwork on your kitty though. If you work full time, I would consider looking around to see if there are any vets with hours that are open late. Most vets also have weekend hours. Also, many vets will let you drop your pet off on your way to work in the morning and pick them up on your way home, if you cannot make an appointment time. So I would look into all these options. In the meantime, I would make sure Red is able to get enough food by locking the cats in separate areas at least part of the day with their food so that you can be sure he is actually eating and that he isn't losing weight because he isn't getting food. But really, with rapid weight loss and diarrhea like this in an older cat, he needs to be seen to determine why it is happening.
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