Approximately 10% of cats over age 10 develop hyperthyroidism, an overactive thyroid gland that causes weight loss, increased appetite, hyperactivity, and eventually serious organ damage if untreated. It is the most commonly diagnosed hormonal disorder in older cats. The good news: it is treatable. The bad news: treatment requires a long-term commitment of time and money.
Signs and symptoms
- Unexplained weight loss despite increased appetite
- Increased thirst and urination
- Hyperactivity, restlessness, or vocalizing more than usual
- Vomiting or diarrhea
- Dull, unkempt coat
- Rapid or irregular heartbeat
- Weakness in the rear legs
- Enlarged thyroid gland (sometimes palpable in the neck)
Treatment options and costs
| Treatment | Estimated cost |
|---|
| Methimazole medication (daily pills or ear gel) | $30-$80/month ongoing |
| Regular bloodwork monitoring | $100-$200 every 3-6 months |
| Prescription y/d thyroid diet (Hills) | $60-$100/month |
| Surgical thyroidectomy | $1,500-$3,000 |
| Radioactive iodine therapy (curative, one-time) | $1,200-$2,500 |
Pet insurance and this condition
Insurance coverage
Pet insurance covers hyperthyroidism if it develops after enrollment and after the standard illness waiting period (typically 14 days). Because hyperthyroidism typically appears in older cats, enrolling early before any thyroid-related symptoms appear is critical. Once diagnosed, it is an incurable chronic condition that will be excluded from any new policy as pre-existing. Ongoing medication costs ($30-$80/month) and monitoring bloodwork are covered under most accident and illness plans.
Insurers worth considering
Embrace
Covers hyperthyroidism and ongoing medication; diminishing deductible rewards healthy years before diagnosis
Healthy Paws
No annual payout limit; covers radioactive iodine therapy ($1,200-$2,500) and ongoing management
Lemonade
Competitive premiums for cats; fast AI claims for recurring medication reimbursements
ASPCA
Covers chronic conditions including hyperthyroidism; includes dental disease common in older cats
Key takeaways
- Hyperthyroidism affects 10% of cats over age 10, making early enrollment especially important
- Radioactive iodine therapy is curative and costs $1,200-$2,500, covered if not pre-existing
- Ongoing medication costs $30-$80/month and is covered under most plans
- Enroll before age 7-8 to ensure coverage if hyperthyroidism develops later
- Once diagnosed, it becomes a permanent pre-existing condition on future policies
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Cost estimates are based on US national averages and may vary significantly by location, specialist, and severity. This guide is for informational purposes and is not veterinary advice. Consult your veterinarian for diagnosis and treatment decisions.