Reasons Why a Cat Loses Weight and Hair

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Cats can experience health problems that cause hair and weight loss.
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It can be worrisome if you see your cat losing hair and weight, especially if your cat seems to be eating well but is still losing weight. There are several reasons why a cat loses weight and hair, and some of them are medical conditions that can be taken care of easily, while others may require an adjustment to your cat's diet.

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Cat hair loss treatment

The right cat hair loss treatment will depend on what is causing the hair loss. Your vet will need to check your cat over thoroughly to determine the cause. It could be as simple as a bad case of fleas which is causing itching and hair loss. It could be something like ringworm or a parasite, which would require a different treatment, says Purina. If there's an underlying health concern, your vet may take a blood sample to find out what is causing it. Alternatively, they may take a blood sample to look for underlying diseases that could be causing your pet's hair loss.

Hyperthyroidism in cats

Hyperthyroidism is an overabundance of thyroid hormone that results in greatly increased metabolism. Hyperthyroidism is the most common reason for why you might say to yourself, "My cat is losing weight but eats constantly." That's the first thing your vet will check for if a cat has a good appetite and may otherwise seem normal but keeps losing weight.


Often, you may not even realize your pet is sick because she may seem normal in all other ways, says Healing Paws Veterinary Care. Keep an eye out for increased thirst, restlessness, and begging for food or attention. Other symptoms include vomiting and diarrhea or urinating outside of the litter box. It can be treated through medication.

Cancer in cats

Cancer can cause weight loss and possibly hair loss in cats, according to Kingstowne Cat Clinic. Cancer is a common cause of rapid weight loss in cats. Typically cancer-related weight loss will also be accompanied by loss of appetite and lethargy.


Hair loss from allergies

Allergies to cat food can be a reason for a cat losing hair and weight, says VCA Hospitals. In a food allergy, the cat's body responds with symptoms such as itchiness. Just about any component in the food, including beef, fish, chicken, and dairy products, can cause an allergic reaction. Food allergies can develop at any time during a cat's life and some cats just seem genetically predisposed to food allergies.

Food allergies cause year-round itching and can result in your cat pulling out fur and losing weight. The itchiness can be so extreme that cats over-groom themselves and cause significant hair loss. Gastrointestinal issues such as vomiting or diarrhea can also appear in addition to skin issues. This may lead to weight loss.


Fleas or parasites

Parasites such as hookworm or roundworm can cause gastrointestinal distress and weight loss in even mild cases. The Cornell Feline Health Center says roundworms are the most common intestinal parasite of cats, affecting up to 75 percent of cats and even higher rates in kittens. These types of parasites live in the cat's intestines and survive by eating food the cat eats.

The Veterinary Cat Clinic says that some cats are very sensitive to fleas. Fleas are so common that it is hard for any cat owner to avoid them completely. If a cat is sensitive to flea bites, they can develop extremely itchy and irritated skin which can lead to hair loss. Fleas can be carriers of another parasite called tapeworm.


Adult tapeworms embed themselves in a cat's small intestine and absorb nutrients eaten by the host. Tapeworm infections rarely cause significant disease in cats but they can cause weight loss.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.