Unexplained Weight Loss in Dogs
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
Losing weight while eating normally can signal malabsorption, diabetes, cancer, or organ disease. Weigh monthly and book a vet exam if loss exceeds 10% body weight.
Red flags
Muscle wasting, poor coat, increased thirst, or vomiting.
Common causes
Parasites, EPI, kidney disease, and neoplasia.
Diagnosis
Blood work, faecal tests, and imaging as indicated.
Related: Pancreatitis in dogs · Senior dog care
Frequently asked questions
Can stress cause weight loss?
Yes — but medical causes must be ruled out first.
Do old dogs lose weight normally?
Some muscle loss occurs with age — rapid loss is not normal.
Can worms cause weight loss?
Heavy parasite burdens can — faecal testing helps.
Should I increase food?
Not until your vet identifies the cause — some conditions need special diets.