Why is my cat suddenly gaining weight and aggressive to other cats?

These sudden changes in temperament and the weight loss are commonly due to an endocrine problem called hyperthyroidism. The thyroid starts working more than normal increasing the metabolism (that is the cause of the weight loss) and causing behavioural changes similar to what you described. A clinical examination at your local veterinarian is essential to confirm this clinical suspicion and treat appropriately. A blood test and urine analysis are needed. Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further. If this answer was helpful please let us know, this will be used to improve our service!

Your kitty is not feeling well. I suggest you take her to a veterinarian for a check up and blood tests. She may be ill, and therefore defensive when the other cats come near her. She may also need special food to gain weight properly .

Thanks for using Petco Pet Education Center, formerly Petcoach! This can due to discomfort so if that is the case now that she is on gabapentin she may do better. Unexpected aggression is a classic sign of pain or discomfort. Hopefully she improves on the gabapentin. If she does not, it is very important to let your veterinarian know so they can keep checking what may be wrong with her. The same underlying condition may be what is causing her weight loss which is important though not that significant. I hope she gets better soon!

Thanks for visiting Petcoach! In a situation like this where your pet is always seemingly hungry and eating other pets food, you want to first rule out any underlying disorder that can cause an increase in appetite, including Diabetes Mellitus. I would first get some baseline bloodwork done at your local vet to do a good overall health check. Then if she comes up clear for any underlying condition, I would recommend getting her on a food that is going to make her feel fuller longer. My top recommendation here is the Royal Canin Feline satiety. This is a prescription food however, so you willl need to get a prescription card through your vet in order to purchase the food from your local pet store. https://www.petco.com/shop/en/petcostore/product/royal-canin-veterinary-diet-satiety-support-dry-cat-food Her urinating outside the litterbox may be related to an underlying UTI or it also may be signs of diabetes, so it is important to get her tested. I hope this helps and best wishes moving forward with your pet Guinevere. I hope you get her appetite and inappropriate urination in control soon. Take care.

Sudden weight loss is always a very big warning light that should not be taken lightly, it's usually a sign of an internal disease that needs to be investigated, i strongly recommend taking him to the vet in order to get it checked, he will need to have a blood test done and possibly an xray as well in order to attempt to diagnose the reason for these symptoms.

There are two very common health issues in older cats that are known for causing a sudden increase in appetite like this: hyperthyroidism, and diabetes. I would definitely recommend taking Lucy to the vet for a check-up when you are able to - he/she can do blood work to check for these problems. If she does have one of these illnesses, they are normally very treatable with medication once a diagnosis is made :)

If this change in your cat’s behavior is recent and sudden then I would be concerned about an underlying problem/illness. I would recommend taking your cat in to be evaluated by your veterinarian to ensure nothing to serious is going on. Your vet will likely recommend blood work and X-rays if indicated. Your vet can also recommend a diet plan to help him lose weight as well. I hope this helps. Thanks for using Petco Pet Education Center, formerly Petcoach. Best of luck.