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Why is my active cat losing weight despite eating and vet visits?

Updated On September 23rd, 2025

Pet's info: Cat | Mixed Breed | Male | neutered | 11 years and 6 months old | 13 lbs

Help! Male cat loses weight, but still seems active. Started few months ago, vomit once every 1-2 weeks, for some 3-4 times. Cat never vomited before, perhaps once every 1-2 years. Vomit clean and normal. Went to vet. Previous weight 6.3kg, in this visit weight down to 6kg. In parallel, spotted difficulties jumping. Vet said arthritis, special food. Vomiting continued another 2-3 times. Visit vet, said to stop with special food. New weight 5.9kg. No more vomiting. Why continued weight loss?

2 Answers

Most Helpful Answer

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Answered By Dr. Strydom, DVM

Veterinarian

Published on May 28th, 2017

Hi there. The most common reason for a cat to be eating, vomiting and active but still lose weight is an over-active thyroid (hyperthyroidism). This can be easily diagnosed with a blood test. Please bring that up to your vet and request the test. It is very easy to do and an easy thing to rule out. If he does have hyperthyroidism it can be treated. Here is a link to an article regarding this disease in cats: http://www.peteducation.com/article.cfm?c=1+2130&aid=218 I hope this helps. Best wishes to you and Kitch. Dr. Amber

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    Answered By Ricardo Fernandez, DVM

    Veterinarian, Veterinary Oncology Resident

    Published on November 12th, 2018

    Thanks for using Petco Pet Education Center, formerly Petcoach! This is something that could happen with a lot of conditions. The most common condition that can cause an increased appetite with continued weight loss is hyperthyroidism. This is something that is diagnosed with a simple blood test. Therapy is usually with medications to begin with. I recommend you consider visiting your veterinarian for further assessment and treatment. Good luck and have a great day!

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