Monitor — routine vet appointment
Hyperthyroidism in older cats
Older cat eating ravenously but losing weight, drinking more, or restless and vocal — book a vet appointment for thyroid testing.
Recognise the signs
- Weight loss despite increased appetite
- Drinking and urinating more
- Restlessness, vocalising at night
- Poor coat
- Vomiting, diarrhoea
- Heart murmur or fast heart rate
- Sometimes only diagnosed on senior bloods
First aid steps
- Book a routine vet appointment with bloods.
- Note specific changes — weight, food intake, behaviour.
Do NOT
- Do not assume increased appetite is good news in an old cat losing weight.
- Do not start human thyroid supplements.
When to phone the vet immediately
- Severe weight loss, vomiting, weakness
- Heart issues alongside (saddle thrombus risk)
Common causes
- Benign thyroid gland enlargement, common in cats over 10
What the vet will need to know
- Weight history
- Appetite, drinking, behaviour changes
- Other ongoing conditions
Aftercare
- Treatment options: daily medication (methimazole), prescription diet (Hill's y/d), surgery, or radioactive iodine treatment.
- Regular blood tests to monitor.
- Watch for unmasked kidney disease as thyroid is treated.
Prevention
- Annual senior bloods from age 8 catch early disease.
Frequently asked questions
Can hyperthyroidism be cured?
Radioactive iodine treatment is curative for most cats and is the gold standard where available. Other options manage but do not cure.
Why does my cat seem hungry all the time?
Overactive thyroid speeds metabolism — the cat burns calories faster than it can eat, hence weight loss with ravenous appetite.
Is it serious if untreated?
Yes — untreated hyperthyroidism damages the heart, kidneys, and overall body condition. Treatment is highly effective.