Why is my cat losing weight?

If you've noticed your cat suddenly losing weight, it may be a symptom of an underlying condition or illness. Here are some of the most common problems.
Adult Abyssinian standing indoors looking away from a white bowl.

Your cat’s weight will naturally change from kitten to adult, affected by factors as varied as its sex, breed, age, lifestyle and diet. But if you notice a sudden drop in your cat’s weight, it’s important to consult a vet as it can be an indicator of a more serious, underlying issue.

Gastro-intestinal disorders in cats

If your cat is suffering from discomfort, pain or irritation in its digestive system, it can lead to a loss of appetite and eventual weight loss as the cat doesn’t want to eat any more. Gastro-intestinal disorders can include irritable bowel disorder (IBD), imbalances of flora in the gut, allergies or problems with how the small intestine is functioning. If it’s the latter, you’ll also notice your cat’s coat and skin are a poorer quality than normal.

Blockages in your cat’s esophagus

Weight loss can also be caused by a blockage in your cat’s esophagus which prevents food from reaching the stomach and being effectively absorbed into its system. This could be a foreign object – one they’ve ingested accidentally – or a physical abscess or growth. Your vet will be able to conduct a thorough examination to determine the problem. Blockages like this are often accompanied by symptoms including refusal to eat, agitation, halitosis, regurgitation and your cat appearing in pain.

Cats and liver disease

Cats don’t often show any clinical signs of liver disease until it is well advanced; however, an early warning sign is weight loss alongside depression, vomiting and refusal to eat.

Adult British Shorthair lying down on a grey sofa.

Your cat and parasites

A number of different parasites can cause weight loss in your cat. Two types, giardia and coccidia, both cause severe diarrhoea which can lead to dehydration and weight loss. A specific version of the second parasite, called toxoplasma gondii, can be passed onto humans, and is ingested when your cat swallows any of the parasite’s cysts which lay on the ground. It’s essential you see a vet if you believe your cat has an infestation, as they’ll be able to specify what parasite it is and how to protect your cat (and you) against it.

Hairballs and cats

Cats spend a significant amount of time grooming themselves, which regulates their body temperature, keeps their hair and skin clean and also helps manage stress. However, if their hair isn’t properly excreted through their digestive system, it can get caught up and form hairballs. These lumps of matted hair can lead to regurgitation, constipation, esophagus blockages, a loss of appetite and eventual loss of weight.

Vitamin deficiencies in cats

Weight loss, alongside dermatological problems like flaking skin, alopecia and scratching, can be an indicator of a B vitamin complex deficiency. This vitamin is water-soluble and cannot be stored in the body, therefore your cat’s diet must include the vitamin B complex to help maintain a healthy coat and skin.

If you have any concerns about your cat’s recent weight loss, make sure to visit your vet; they’ll conduct a full examination and be able to address your concerns directly.


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If you have any concerns about your cat’s health, consult a vet for professional advice.