A hyperthyroid cat on daily methimazole costs USD 785-1,420 a year in the US, GBP 530-1,010 in the UK and CNY 810-2,420 in China, once pills, rechecks and panels are added up. Radioiodine is a single year of USD 1,690-3,300, GBP 1,250-2,450 or CNY 3,700-9,700, and after the 6-month recheck the annual bill drops to a thyroid panel. The two routes converge around year 3.
Two Routes, Two Very Different Bills
Every treatment plan is some mix of 3 things: a daily pill, surgery, or a one-time radioiodine dose. Surgery is rarely chosen now. That leaves the pill route, which is cheap in year one and never stops, and the radioiodine route, which is expensive once and then mostly monitoring. The tables below price both routes over 12 months in 3 currencies, and each total is the sum of the rows above it.
The Pill Route, Line by Line
Methimazole is the standard drug; carbimazole is the same class and is common in the UK. Dosing starts twice daily and often drops to once daily after values stabilise, so a year is 250-500 tablets of 5 mg, or 2-6 bottles. Rechecks carry the rest of the bill: 4-6 visits in year one, each with a T4 and often a full panel.
| Annual line | US (USD) | UK (GBP) | China (CNY) |
|---|---|---|---|
| Methimazole, 250-500 tablets | 90-220 | 70-170 | 240-720 |
| T4 recheck, 4-6 visits | 300-480 | 200-330 | 200-600 |
| Full panel, CBC and biochem, 2-3 | 260-420 | 170-300 | 250-700 |
| Blood pressure and urine protein, 2-4 | 120-260 | 80-180 | 100-320 |
| Pill splitter, gel caps, labels | 15-40 | 10-30 | 20-80 |
| Year total, pill route | 785-1,420 | 530-1,010 | 810-2,420 |
The floor is a cat that stabilises in 4 weeks and needs 4 rechecks; the ceiling is a cat that needs 6 rechecks, 3 panels and a blood pressure check every quarter. Pills are 11-15% of the row total in the US, 13-17% in the UK and about 30% in China, which is the single most useful fact on this page: the drug is not what you are paying for.
Monitoring Is the Real Cost, Not the Drug
Year one runs 6-9 clinic contacts. The first recheck lands 2-4 weeks after starting, the second at 6-8 weeks, then every 3-6 months once values sit in range. Each T4 alone is USD 60-90, GBP 45-70 or CNY 80-180; add a full panel and the visit is USD 130-210. Cats over 10 also need renal values tracked because treating the thyroid can unmask kidney disease, which is why 2-3 panels a year is a floor rather than a luxury.
Radioiodine: One Payment, Three Rechecks
Radioiodine is given as a single treatment during a 2-4 day hospital stay, and the cost is mostly the isolation facility, not the isotope. In the US, USD 1,200-2,400 covers the treatment plus the stay; UK centres run GBP 900-1,800; Chinese referral hospitals run CNY 3,000-8,000. Rechecks fall at 1 month, 3 months and 6 months, then annually. Roughly 85-95% of cats are euthyroid at the 3-month check, and 2-5% need a second treatment, which adds another USD 1,200-2,400 in the year you pay it.
| Radioiodine year | US (USD) | UK (GBP) | China (CNY) |
|---|---|---|---|
| Treatment plus 2-4 day stay | 1,200-2,400 | 900-1,800 | 3,000-8,000 |
| Pre-treatment scan and T4 | 250-450 | 180-320 | 400-900 |
| Rechecks at 1, 3 and 6 months | 240-450 | 170-330 | 300-800 |
| Year total, radioiodine route | 1,690-3,300 | 1,250-2,450 | 3,700-9,700 |
Compare that with 5 years of pills at USD 785-1,420: the pill route totals USD 3,900-7,100 and the radioiodine route totals USD 1,690-3,300 plus 4 annual panels at USD 240-450 each. The option-by-option comparison runs the same arithmetic over 1, 3 and 5 years. Break-even in the US lands between month 22 and month 40.
Why the Pill Year Doubles in the Third Year
Two things drift. Tablets go from once daily back to twice daily in 20-30% of cats as the disease progresses, which pushes the year from 250 tablets to 500. And rechecks never drop below 2 a year, so the floor of the pill route is USD 400-600 before any drug is bought. Year one therefore looks cheap at 785, year three settles at 900-1,200, and year five is 1,100-1,600. Our first year versus later years piece covers the same pattern for other chronic conditions.
The Country Gap: Same Molecule, Different Price
Methimazole is off patent everywhere, so the drug is cheap in all 3 markets: USD 0.35-0.90 a tablet in the US, GBP 0.28-0.68 in the UK, CNY 0.48-2.90 in China. The gap comes from the clinic side. A T4 in the US is USD 60-90, in the UK GBP 45-70, and in China CNY 80-180, which is 3-6 times cheaper in dollar terms. Radioiodine is the opposite: China's 3,000-8,000 CNY translates to USD 420-1,120, below the US floor, because only a handful of referral centres offer it and volumes are thin.
What Pushes a Pill Year From 785 to 1,420
Four levers: 6 rechecks instead of 4 (plus USD 120-180), 3 panels instead of 2 (plus USD 130-210), quarterly blood pressure checks (plus USD 60-120), and a cat that needs compounded liquid or a transdermal gel because it will not take a tablet. Compounding runs USD 40-90 a month, which alone is USD 480-1,080 a year and lands at the ceiling of the range.
Tracking a Thyroid Year
Most owners remember the radioiodine invoice and forget the 6 rechecks. Log every visit and every bottle for 12 months, then divide by 12: USD 65-118, GBP 44-84 or CNY 68-202 a month for the pill route. A cost tracker with 3 fields, date, item, amount, is enough. If the monthly average moves 20% in either direction, the cause is usually a recheck interval that changed, not the drug price.
When the Bill Is Not the Point
Book the clinic the same day for: a resting heart rate over 240 beats a minute, breathing with the mouth open, 5% weight loss in 4 weeks on treatment, vomiting for 2 days, or a new heart murmur. Untreated hyperthyroidism strains the heart and hides kidney disease, and 1 emergency visit at USD 150-400 costs more than a year of rechecks. Ask for the T4 value in writing at every visit; a number you can compare beats a verbal all good.
- Ask for a 6-visit recheck plan in writing: 2-4 weeks, 6-8 weeks, then every 3-6 months.
- Buy 100-tablet bottles and split only with a splitter; uneven halves show up as a swinging T4.
- Keep one folder with every T4, renal panel and blood pressure reading, dated.
- Price the radioiodine route over 3 years, not 1, before you decide between the two.
- Re-check the monthly average at month 6 and month 12, not only when a bill feels large.
Terms mentioned in this article
Frequently asked
Is the pill really cheaper than radioiodine?
In year one, yes, by a wide margin: USD 785-1,420 against USD 1,690-3,300. Over 5 years the pill route totals USD 3,900-7,100 while radioiodine totals USD 1,690-3,300 plus 4 annual panels at USD 240-450 each, so the break-even lands between month 22 and month 40 in US prices. A cat that will not take tablets shifts the maths further toward the one-time treatment.
How many rechecks does a hyperthyroid cat need in the first year?
Plan for 6 visits: 1 at 2-4 weeks after starting treatment, 1 at 6-8 weeks, then every 3-6 months once the T4 sits in range. Budget 2-3 full panels and 2-4 blood pressure checks inside those visits. Rechecks are roughly 82-87% of the annual bill in the US, far more than the 250-500 tablets themselves.
What happens if the first radioiodine treatment does not work?
About 85-95% of cats are euthyroid at the 3-month recheck, and 2-5% need a second treatment, which adds another USD 1,200-2,400 in that year. Rechecks at 1, 3 and 6 months catch the ones that did not respond before the annual review, which is why the 6-month visit is not optional even when the cat looks well.