Why is my indoor/outdoor cat suddenly lethargic and walking stiffly?

These symptoms are definitely of concern and most likely a sign of illness and not depression. It is not any fault of yours, but he does need to see a veterinarian to determine the cause of his illness. They may recommend running bloodwork to check for signs of systemic illness such as kidney disease or infection, and may want to test his for Feline Leukemia and Feline Aids since he was an outdoor cat before he came to you.

Your cat should be examined by a veterinarian for a work up and treatment. There are a lot of diseases that could cause those signs including diabetes, kidney disease, liver disease, gastrointestinal issues, thyroid disease, and cardiac disease. Your vet may need to run lab-work and take X-rays to diagnose.

Poor Milson! Lethargy could be caused by systemic illness, infection, inflammation, or injury. It could also be due to something that he ate outside. Given that he is still eating, I would keep an eye on him for the next 24 hours and if he's still lethargic after this time, then I would have him seen by a vet for a health check.

Thanks for using Petco Pet Education Center, formerly Petcoach! This is possibly neck or back pain. I recommend that you have Kitty reevaluated by your veterinarian for further assessment and treatment since things have not improved. Likely diagnostics include radiographs. Treatment would be based on findings. At the very least they can prescribe pain control medications to make kitty feel better. In the meantime, reduce his activity as much as possible as that in itself can make a big difference. Good luck and have a good day!

He should be examined by your veterinarian. Blood work including a urinalysis should be done to assess major organ function and to diagnose kidney infection or urinary tract infection. Abdominal xrays may diagnose foreign body, masses, bladder/kidney stones or bladder inflammation. Supportive care or pain management may be indicated to keep him comfortable until a diagnose is reached.

Thank you for submitting your question regarding Squeak. If he goes outside daily, there is a chance that he has sustained fight wounds from an altercation with another cat. This is a common cause of the symptoms you have described. Search him over carefully for any swelling beneath the skin. A lot of times a bite wound will heal over trapping the infection underneath. This allows an abscess to develop under the skin. It can be painful and cause a fever in a cat. If this does not appear to be the case, he could have a muscular injury causing pain or an infection such as a cold. He will likely need to see his veterinarian to determine the cause of his lethargy. Keep him indoors and encourage him to eat and drink. I hope this information helps!

Thanks for using Petco Pet Education Center, formerly Petcoach! I'm sorry to hear Jax hasn't been feeling well. Does he go outside? If he does, even if you can't find one right now I would be concerned that he suffered a bite of some kind, as cats can develop abscesses fairly easily when they suffer a trauma. I would be concerned by his behavior, as it does sound like there may be an underlying issue going on, such as an infection, GI upset, or an underlying medical issue (such as kidney disease or diabetes). If he doesn't perk up, start eating and getting some energy back, I would recommend he be evaluated by his regular veterinarian to determine the underlying cause for his change in behavior, have any necessary testing done (xrays, bloodwork) and start any treatment he may need to resolve it. Good luck!