Radioiodine for Cats: 1,200-2,500 and a 3-5 Day Stay

Radioiodine is priced like a procedure and billed like a hospital stay. The injection itself takes under 5 minutes. The bill lands at USD 1,200-2,500 in the United States, GBP 1,000-1,900 in the UK and CNY 8,000-16,000 in China, and it covers 3-5 days of radiation isolation, not 1 afternoon. Three numbers explain the whole invoice: 1 dose, 3-5 nights, 1,200-2,500 dollars. Every other figure below is a detail of those three, and if you are still weighing the 3 routes, the yearly totals sit in the annual cost of a hyperthyroid cat.

1 dose, 3-5 nights, 1,200-2,500

A cat gets 1 subcutaneous injection of iodine-131, usually 1-5 mCi, with the activity set by thyroid size, total T4 and scan uptake. There is no daily tablet, no second visit for the dose and no taper. The stay exists because the cat keeps excreting isotope: iodine-131 has a half-life of 8.02 days, and a cat is usually discharged on day 3-5, when the dose rate at 1 meter falls low enough for a household. That is the 3-5 in the price. The 1,200-2,500 is not the injection either; it is the panel, the scan, the dose, the nights and 3 rechecks stacked together. Because the payment is a single event, the arithmetic that matters is a payback period rather than a monthly bill, and the dose-by-dose payback math covers that side of the choice.

The invoice, line by line, in 3 regions

These are 2026 figures for a mid-tier city practice, and the 5 line items sum to the headline in each column, which is the point of showing them.

Line item	US (USD)	UK (GBP)	China (CNY)
Chemistry, CBC, total T4, urinalysis	150-300	120-250	800-1,800
Thyroid scan or uptake measurement	200-400	170-330	1,200-2,600
Radioiodine dose, 1-5 mCi, plus injection	450-800	380-720	3,500-6,500
3-5 nights of isolation and boarding	250-650	200-440	1,700-3,600
3 rechecks at 1, 3 and 6 months	150-350	130-160	800-1,500
Total, first 6 months	1,200-2,500	1,000-1,900	8,000-16,000

The arithmetic is worth doing once by hand. In the US column, 150 + 200 + 450 + 250 + 150 is 1,200, and 300 + 400 + 800 + 650 + 350 is 2,500. The UK column runs 1,000 to 1,900 and the China column 8,000 to 16,000 on the same 5 rows. If a clinic quotes 900 dollars for the whole package, ask which row it dropped; the isolation line disappears most often, and so does the scan.

Why the same treatment costs 1.5-3 times more 20 minutes away

Each row above swings by a factor of 1.5 to 3 between practice types. A thyroid scan at 200 dollars in a suburban clinic is 400-600 at a teaching hospital. Isolation is billed per night at 50-130 dollars, so a 5-night stay costs 2.5 times a 3-night one before the dose changes at all, and a practice with 2 isolation rooms charges more than one with 6. Because all 5 rows move together, the total moves with them. Take 0.7 times the bottom of 1,200 and you get 840; take 1.4 times the top of 2,500 and you get 3,500. The realistic envelope for 1 cat in 1 American city is 840-3,500 dollars, and for that reason a quote without line items cannot be compared to anything. Put 2 competing quotes into the cost tool before you choose, because the lower headline is often the quote that dropped 2 rows.

What the quote usually leaves out

Three costs sit outside the 1,200-2,500 and appear on a separate invoice. An abdominal ultrasound at 150-300 is common before radioiodine in a cat over 10, because the thyroid panel does not show a adrenal or kidney mass. A cardiac echo at 200-400 is standard if there is a murmur, and a cat with untreated hyperthyroid heart disease can decompensate in the 2 weeks after treatment. A methimazole trial of 4-8 weeks at 30-60 a month is often used first, both to confirm the diagnosis and to see whether kidney values hold once the thyroid is suppressed. Add all 3 and a first-year bill can reach 1,700-3,500 before the rechecks.

What the 3-5 days actually buy

The cat is not sick during the stay. It is radioactive, and the rules are about other people. Most protocols send a cat home when the reading at 1 meter is under 0.5 mR/hr, which normally happens on day 3 to day 5. At home, expect 7-14 days of handling limits: double-bag litter for the first 48-72 hours, no sleeping in the same bed, no lap sitting for more than 10-15 minutes a day, pregnant women and children under 12 kept out of the room, and gloves for cleaning the box. A cat that urinates on a rug in the first 2 days creates a cleanup problem no clinic warns you about.

The 150-350 of rechecks you should not skip

Three visits at 1, 3 and 6 months, each a total T4 at 50-120 plus an exam at 50-90. The reason is not the thyroid. In 20-30% of treated cats, kidney disease shows up in the first 6 months, because a high thyroid hormone had been inflating renal blood flow and hiding it. Creatinine, SDMA and urine specific gravity at each visit tell you whether the cure uncovered a CKD that was always there. A T4 falling from 12 to 1.2 ug/dL in 6 weeks is a cure, not an overdose, and about 5% of cats need a second dose at 800-1,500 dollars.

When radioiodine is the wrong purchase

Methimazole at 30-60 a month plus 4-5 T4 tests a year lands at 650-1,400 a year. Divide 1,200 by 55 a month and the payback is 22 months; divide 2,500 by 30 and it is 83 months. A 15-year-old cat with a heart murmur and IRIS stage 3 kidney disease may never reach break-even, and the radiation hold may not be safe for it. Delay or skip radioiodine when creatinine is already over 2.5 mg/dL, when the goiter is larger than 4 cm and pressing on the trachea, when the cat cannot be boarded 3-5 days, or when nobody at home can follow 7-14 days of handling limits.

Before you pay: 5 checks

Ask for the 5 line items in writing, with the number of isolation nights stated as 3, 4 or 5, not as a range.
Confirm the recheck price is included or budget 150-350 on top of the quote.
Get a T4, creatinine and blood pressure within 14 days of the dose, because the dose depends on all 3.
Ask whether a second dose at 800-1,500 dollars is covered by the same price if the first one under-treats, which happens in about 5% of cats.
Ask for the discharge reading at 1 meter in writing, so you know when the 7-14 day handling window starts.

Terms mentioned in this article

T4 CKD SDMA

Frequently asked

Does the 1,200-2,500 include the thyroid scan and the rechecks?

In the itemized totals above, yes: the panel at 150-300, the scan at 200-400, the dose at 450-800, 3-5 isolation nights at 250-650 and 3 rechecks at 150-350 add up to 1,200-2,500 in the US column. Plenty of clinics quote the dose and the nights only, so ask for the 5 rows in writing and check whether the scan and the 6-month recheck are inside the number.

Why is the hospital stay 3-5 days instead of 1?

Because the cat is radioactive, not because it is recovering. Iodine-131 has a half-life of 8.02 days, and most protocols discharge when the dose rate at 1 meter is under 0.5 mR/hr, which usually takes 3-5 days. Some states also set a legal minimum hold, so the 3-5 day figure is a mix of physics and regulation rather than clinical need.

Is radioiodine cheaper than a tablet every day?

Not in year 1, and not always at all. Methimazole runs 30-60 a month plus 4-5 T4 tests a year, about 650-1,400 annually, while radioiodine is 1,200-2,500 once. Divide the total by the monthly drug cost and break-even lands at 22 to 83 months, so an older cat with kidney disease may never recover the difference in cash terms.