Why is my cat losing weight but still eating?
If your cat is eating normally or even more than usual but still losing weight, hyperthyroidism is one of the most common explanations — particularly in cats over eight years of age. The overactive thyroid gland produces excess hormones that accelerate metabolism faster than food intake can compensate, causing progressive weight loss despite a healthy or increased appetite.
MaxPetz in Delhi offers veterinary consultations for senior cat health, including diagnosis and management of feline hyperthyroidism. If your cat is losing weight unexpectedly, a clinical examination and blood panel can identify the cause quickly.
Key point: Weight loss in a cat that is still eating is rarely normal. It warrants a vet visit — do not wait to see if it resolves on its own.
What are the signs of hyperthyroidism in cats?
Feline hyperthyroidism produces a recognisable cluster of signs. Because the condition develops gradually, owners often attribute early changes to normal ageing. Knowing what to look for helps you act sooner.
- Unexplained weight loss despite normal or increased food intake
- Increased appetite (polyphagia) — some cats seem insatiably hungry
- Increased thirst and urination
- Hyperactivity, restlessness, or irritability — unusual in an older cat
- Vomiting or diarrhoea, sometimes with undigested food
- Unkempt, matted, or greasy coat
- Rapid or irregular heartbeat (detectable by a vet on examination)
- Muscle weakness or difficulty jumping
- Occasional difficulty breathing if the heart is affected
Warning: Rapid breathing, open-mouth breathing, or collapse in a cat with suspected hyperthyroidism is a medical emergency. Seek veterinary care immediately.
Why do cats develop hyperthyroidism?
Hyperthyroidism occurs when one or both lobes of the thyroid gland enlarge and produce excess thyroxine (T4). In the vast majority of cases the cause is a benign overgrowth of thyroid tissue called adenomatous hyperplasia. Thyroid carcinoma (malignant tumour) accounts for a small minority of cases.
| Factor | Detail |
|---|---|
| Age | Most cases occur in cats aged 8 years and older; average age at diagnosis is around 12–13 years |
| Breed | Siamese and Himalayan breeds appear to have a lower incidence; no breed is fully protected |
| Diet | Some research associates high fish or liver-based diets and certain canned food compounds with increased risk, though a definitive cause has not been established |
| Environment | Indoor cats and those exposed to certain household chemicals have been studied, but no single environmental trigger is confirmed |
How is hyperthyroidism in cats diagnosed?
Diagnosis is straightforward when clinical signs are present and confirmed with blood tests. A vet at MaxPetz Delhi will typically follow this pathway:
- Physical examination — palpation of the neck to detect an enlarged thyroid gland (goitre), assessment of heart rate, body condition score, and coat quality
- Total T4 blood test — a single serum thyroxine measurement is the primary diagnostic test; an elevated result in a cat with compatible signs confirms hyperthyroidism in most cases
- Complete blood count and biochemistry panel — to assess kidney function, liver enzymes, and overall health before starting treatment
- Urinalysis — hyperthyroidism can mask underlying chronic kidney disease; urine specific gravity helps evaluate renal function
- Blood pressure measurement — hypertension is a common secondary complication
- Cardiac assessment — if a murmur or arrhythmia is detected, an echocardiogram may be recommended
In borderline cases where T4 is within the upper normal range but clinical suspicion is high, a free T4 (fT4) test or repeat testing after a short interval may be advised.
What is the treatment for hyperthyroidism in cats?
There are four recognised treatment options. The right choice depends on the cat's age, overall health, kidney function, and owner circumstances. A vet consultation is essential before starting any treatment.
| Treatment | How it works | Key consideration |
|---|---|---|
| Oral medication (methimazole / carbimazole) | Blocks thyroid hormone production; given daily or twice daily | Requires lifelong administration and regular monitoring; does not cure the underlying gland change |
| Transdermal gel | Same drug applied to the inner ear flap; useful for cats that resist pilling | Slightly lower absorption than oral; ear rotation required |
| Surgical thyroidectomy | Removal of the affected thyroid lobe(s) | Can be curative; requires stabilisation with medication first and carries anaesthetic risk in older cats |
| Dietary management (iodine-restricted diet) | A prescription low-iodine diet limits thyroid hormone synthesis | Effective only if the cat eats exclusively this diet; not suitable for multi-cat households without strict feeding separation |
Important: Kidney function must be re-evaluated 4–6 weeks after starting treatment. Treating hyperthyroidism can unmask pre-existing chronic kidney disease, which may influence the long-term management plan.
When should you be concerned about your cat losing weight?
Not every fluctuation in a cat's weight is an emergency, but certain patterns require prompt veterinary attention. Book a consultation at MaxPetz Delhi if you observe any of the following:
- Your cat has lost noticeable body weight over 2–4 weeks despite eating the same amount or more
- Weight loss is accompanied by increased thirst, frequent urination, or vomiting
- Your cat is aged 8 years or older and showing any behavioural change alongside weight loss
- The coat has become dull, matted, or greasy without an obvious grooming problem
- You can feel the spine or hip bones more prominently than before
- Your cat seems restless, vocal at night, or unusually irritable
- There is any change in breathing rate or effort
Weight loss of more than 10% of body weight is considered clinically significant in cats and always warrants investigation, regardless of other signs.
How does MaxPetz Delhi support cats with hyperthyroidism?
MaxPetz in Delhi provides veterinary consultations for feline hyperthyroidism and senior cat health, combining clinical examination with diagnostic blood panels to reach an accurate diagnosis. The team uses cutting-edge technology and a compassionate approach to guide owners through treatment choices — whether that is long-term medication management, dietary therapy, or surgical referral — and supports ongoing monitoring to protect kidney function as treatment progresses.
For cats with complex or concurrent conditions, the clinical team coordinates a care plan that accounts for the whole patient, not just the thyroid result. Use the Doctor Consultation booking form on this page to arrange an appointment, or explore our Senior Cat Health services for broader wellness support for older cats.
Book a consultation at MaxPetz Delhi
Use the booking form on this page to arrange a vet consultation for your cat's weight loss or thyroid concerns.