Young cat with a swollen belly on a vet exam table while the veterinarian gently feels its abdomen

Cost Guide

FIP Treatment Cost: $4,000-$9,000 for GS-441524, and Does Insurance Cover It

Marcel JanikNov 9, 2026 · 9 min read

Five years ago an FIP diagnosis meant choosing a day. Now it means 84 days of an antiviral and a bill of $3,000-$8,000 for the drug alone, $4,000-$9,000 with the diagnosis and the blood tests that follow. The drug is a prescription product in the US since June 2024, but it is still not FDA-approved, and that one word decides whether your insurer pays. Here is the bill, the odds, and the questions to ask before you sign anything.

What FIP Is, and Why the Diagnosis Alone Costs $400-$1,000

FIP starts as a harmless gut virus. Feline coronavirus is everywhere cats live together; the European ABCD guidelines call it ubiquitous and say most infected cats are healthy or have a mild bout of diarrhea. In a minority the virus mutates inside the cat and triggers a runaway inflammation of blood vessels. The guidelines put the share of coronavirus-infected cats that go on to develop FIP at up to 12%, with young cats, crowded homes and stress as the drivers. Our FIP page covers the wet and dry forms and the symptoms.

There is no single test, which is why diagnosis is a $400-$1,000 line before any treatment. From our cost data: fluid analysis if there is belly or chest fluid (a yellow, sticky, protein-rich sample is the strongest clue), a blood panel showing high globulins, a coronavirus PCR, and abdominal ultrasound at $300-$500. The ABCD guidelines are blunt that an ante-mortem diagnosis can be difficult, and for cats without fluid there was no non-invasive confirmatory test. Vets now treat on a strong clinical picture rather than waiting for certainty, because the treatment itself is the test: a cat that responds within days almost certainly had FIP.

Neurological and ocular FIP cost more to diagnose and to treat. The dry form in the brain or eyes may need an MRI or a specialist ophthalmology exam, and later a higher drug dose. Budget for the top of every range if your cat has wobbling, seizures or cloudy eyes.

The Drug - $3,000-$8,000 for 84 Days, and Where It Comes From Since 2024

GS-441524 is the active form of remdesivir, and in cats it works. The first field trial, Pedersen and colleagues at UC Davis in 2019, treated 31 cats with naturally occurring FIP. Five died early with severe disease; of the 26 that completed at least 12 weeks, 18 stayed healthy after one round and the rest relapsed, and after retreatment at a higher dose there were 25 long-term survivors. The study settled the protocol most vets still use: 4 mg/kg under the skin once a day for at least 12 weeks, which is where the 84 days comes from.

The bigger real-world dataset is British. Taylor and colleagues followed 307 cats treated between 2020 and 2022 with legally compounded remdesivir and GS-441524 from a UK pharmacy. Median treatment length was 84 days. At the end of follow-up 84.4% of the cats were alive, 10.8% relapsed, and the most common side effect was pain at the injection site in almost half the cats given injectable remdesivir, which is one reason oral tablets took over. Cats that responded fully within the first 30 days were significantly more likely to survive the course.

What it costs and why the range is wide. The dose is by weight and the course is 84 days, so a 2 kg kitten costs far less than a 6 kg adult, and neurological cases need a higher dose. Our data puts the drug course at $3,000-$8,000, with neurological FIP pushing the total toward $8,000-$12,000. Where you get it: until 2024, US owners bought unregulated product from online groups. On May 10, 2024 the FDA announced it would not enforce approval requirements for GS-441524 compounded for a specific cat on a veterinarian's prescription, while stating plainly that such compounded drugs remain unapproved. Stokes Pharmacy, with the Bova Group, began shipping a compounded oral tablet on June 1, 2024, on prescription only, as the Cornell Feline Health Center notes. The drug is still not FDA-approved. Keep that sentence for the insurance section.

Cat receiving its daily oral FIP medication at home

After the 84 Days - Monitoring, Relapse and the Full Total

The course does not end when the tablets do. Standard practice is 12 weeks of observation after treatment with blood work at intervals, because relapses cluster in that window. Pedersen's relapses came between 3 and 84 days after stopping; Taylor's 10.8% relapse rate includes cats that relapsed during and after the course. Each recheck with a blood panel runs $100-$250, and a relapse means a second course at a higher dose, which is the scenario that takes a $5,000 case past $10,000.

The full total from our data: $4,000-$9,000 for diagnosis, an 84-day course and monitoring in a straightforward wet or dry case. Compare that with the cost of the alternative, which five years ago was euthanasia within weeks. Most owners who can find the money find it; the point of this article is that you can know the number on day one instead of discovering it at week six.

Ways the bill moves. Oral tablets are easier than injections and avoid the injection-site pain the UK study recorded, but ask what the per-tablet price works out to at your cat's weight. Treating early, while the cat still eats, avoids hospitalization for fluids and feeding, which from our emergency-visit data adds $800-$3,000 before the FIP drug is even started. And a cat under 2 kg simply costs less to dose than one over 5 kg.

Does Pet Insurance Cover FIP? The Unapproved-Drug Question

FIP itself is an illness and is covered like any other on an accident-and-illness policy, as long as the cat was enrolled and past the 14-day waiting period before the first signs, and no earlier vet note mentions fever, weight loss or fluid. The diagnostics, ultrasound, hospitalization and rechecks are routine claims. The problem is the drug.

GS-441524 is a compounded, unapproved drug, and that is the clause to read. Many policies reimburse prescribed medications; some exclude experimental or unapproved treatments or limit compounded drugs. Which side of that line your insurer puts GS-441524 on is a question for them, in writing, before the first tablet. Ask two things: whether compounded drugs prescribed by your vet are reimbursed, and whether there is an exclusion for drugs not FDA-approved. Our guide to common exclusions shows how that wording usually looks, and how pet insurance works walks the reimbursement formula on a real bill.

The timing trap is sharper with FIP than most diseases. The typical patient is a kitten or a young cat from a shelter or breeder, often insured at adoption. A note of "mild fever, monitor" or "soft stool" at the first wellness visit can be argued into a pre-existing sign months later. Enroll on day one, keep the first visits clean and documented, and if the cat is from a multi-cat environment, treat the first unexplained fever as the emergency it may be.

FIP Treatment Cost - Common Questions

How much does FIP treatment cost?

The 84-day GS-441524 course runs $3,000-$8,000 depending on the cat's weight and the form of FIP. Diagnosis adds $400-$1,000 and monitoring after treatment adds several hundred. Typical total: $4,000-$9,000. Neurological FIP can reach $8,000-$12,000.

What is the success rate of GS-441524 for FIP?

In the UC Davis field trial, 25 of 31 cats became long-term survivors after one or two courses. In a 2023 UK study of 307 cats treated with legally compounded remdesivir and GS-441524, 84.4% were alive at the end of follow-up and 10.8% relapsed.

Is GS-441524 legal in the United States?

Since May 10, 2024 the FDA has said it will not enforce approval requirements for GS-441524 compounded for a specific cat on a veterinarian's prescription, while noting such compounded drugs remain unapproved. A compounded oral tablet has been available by prescription since June 1, 2024. It is not FDA-approved.

Does pet insurance cover FIP treatment?

FIP is covered as an illness if the cat was enrolled before any signs. The uncertainty is the drug: GS-441524 is compounded and unapproved, and some policies exclude unapproved or experimental treatments. Ask your insurer in writing whether compounded, non-FDA-approved drugs prescribed by your vet are reimbursed.

How long is FIP treatment?

At least 12 weeks, usually 84 days of daily oral or injectable medication, followed by about 12 weeks of observation with blood tests. Relapses are treated with a second course at a higher dose.

Can FIP come back after treatment?

Yes. Roughly one in ten cats relapses, mostly within the 12 weeks after treatment ends. Neurological relapses are the hardest to treat and need a higher dose. Cats that respond fully within the first 30 days are the most likely to stay in remission.

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