Why is my cat losing weight after a new cat joined? Stress or age?

Thanks for visiting Petcoach. A lot of vets have a hard time assessing an overweight cat during an exam, mainly because some cats have a short temper and we are working against the clock in a lot of these cases. So sometimes we cannot feel for the ribs, spine, etc. It is very possible that Jasper was overweight to begin with and now is more ideal weight. Without a photo attached it is hard to tell, but as long as his other faculties are intact (i.e. eating well, normal stools), then I would not worry about the weight loss. The weight control food is limiting his calorie intake, and with his activity level, he is likely just going back down to his normal standard weight. He should level off with he weight loss once he has reached his ideal weight soon, if this is the case. Here is a website link so that you can assess his BCS (body condition score) yourself at home https://www.wsava.org/WSAVA/media/PDF_old/Body-condition-score-chart-cats.pdf If however, you are still concerned about his weight loss, and he seems overly hungry, then I would be suspicious of underlying thyroid disease. A thyroid test would be next on the agenda if he meets these criteria. Thyroid disease is typically easily managed in cats and he is of the age where we do see more of this disorder. i hope that Jasper's weight loss is attributed to his new food and that he starts to level off with his weight soon! Best wishes and take care.

It is concerning that Luna has had a change in behavior and has lost weight. While it can take time for a cat to adjust to a new member of a household, it's an extreme reaction to lose weight. I would be concerned that she may have an medical illness causing her change in behavior. Lethargy and anorexia are unfortunately very general signs of illness and can be caused by systemic illness, infection, inflammation, or injury. I'd recommend a visit to the vet this weekend. The vet can diagnose if there is medical cause behind these symptoms, and can discuss treatment with you if there is one. Good luck, I hope this helps!

Thanks for using Petco Pet Education Center, formerly Petcoach! I’m glad to hear Grippet has lost the weight you wanted him to, but at his age we would want to ensure all the weight loss is for healthy reasons and not an underlying medical issue. As cats age, they frequently can get an overactive thyroid, diabetes, or kidney issues (among others) that can lead to unhealthy weight loss. I would recommend he be evaluated by his regular veterinarian and have bloodwork done to ensure all his weight loss is healthy and there isn’t an underlying issue that needs to be addressed. Good luck!

Since you adopted a new dog, this could be due to stress but it could also be due to a medical condition like hyperthyroidism or diabetes. I recommend having Rosie seen by a vet for a geriatric blood panel and urinalysis. I hope this helps!

Hi there and thank you for using Petco Pet Education Center, formerly Petcoach to address your concern. There is a lot that we cannot tell from an examination on a pet, especially if it is something like sudden weight loss but the pet is otherwise acting normal. I would recommend having Kini's blood tested to evaluate overall systemic functions and see if there is an explanation for the weight loss. Check thyroid level as well. If all is normal on blood but the weight continues to fall, I would recommend x-rays and an abdominal ultrasound. I hope this helps! Please let me know if you have any other questions or concerns and I would be more than happy to help you further.

Yes, I would definitely be concerned about Joey. Rapid weight loss can be a sign of a medical illness, and it's certainly not normal for a cat to lose this much weight so quickly without any changes in diet. Weight loss can be a very general sign of illness, and it could be caused by dental disease, systemic illness, infection, kidney disease, hyperthyroidism, diabetes inflammation, injury, or even cancer. I would take him into the vet first thing Monday for a physical exam, blood tests, and urinalysis. The vet can diagnose what has caused his rapid weight loss and how best to treat it. Good luck, I hope this helps!

Weight loss is possible due to increased activity, but 9kg to 4kg is more drastic than I would expect. I would discuss doing bloodwork with your vet. Increased activity and weight loss is common in cats with hyperthyroidism. Weight loss can also be caused by kidney disease and diabetes. All 3 of these conditions can be diagnosed with simple bloodwork (CBC, chemistry, thyroid panel) and urinalysis.