Unexplained Weight Loss in Cats
Veterinary references checked with PetHealth+ · Last reviewed June 2026
By Kaiser Khan , Founder Veterinary references checked with PetHealth+ ( process ) Last reviewed Cite this page How we research & review
Cats losing weight while eating can have hyperthyroidism, diabetes, kidney disease, or cancer. Any unintentional loss deserves blood tests — especially in cats over 8 years.
Why cats lose weight
Increased metabolism (hyperthyroid), malabsorption, and chronic disease.
Appetite changes
Some cats eat more yet lose weight with hyperthyroidism.
Action
Weigh regularly — kitchen scales detect small changes.
Related: Hyperthyroidism in cats · Diabetes in cats
Frequently asked questions
Can dental pain cause weight loss?
Yes — painful mouths reduce eating.
Do worms cause weight loss?
Heavy burdens can — faecal tests help.
Is weight loss normal in old cats?
No — investigate rather than accept as ageing.
How fast is dangerous?
More than 10% body weight loss warrants prompt testing.