What FIP treatment costs in the UK, 2025-26: an honest look

The first thing to understand is why nobody can give you one clean figure, because once you see it, the ranges make sense.

The dose is based on weight. FIP antivirals are dosed per kilogram, so a large adult cat needs more medicine each day than a small kitten, and costs more to treat over the same course (Taylor et al., 2025).

The form of FIP changes the dose. Cats with ocular or neurological FIP are usually given a higher dose, because the drug has to cross into the eye and the brain, so those cases cost more than a straightforward wet or dry case (Taylor et al., 2025).

A growing kitten's cost climbs as it grows. This one catches people out, so it is worth dwelling on. FIP most often strikes young, growing kittens, and because the dose tracks weight, the dose goes up as the kitten gains weight through the course, which means the cost goes up too. It is not a hidden charge or a vet padding the bill. It is the same reason the treatment works: the dose is being kept correct for a cat that is getting bigger. We explain the why, and why it matters clinically, in weigh weekly, re-dose weekly. For your budgeting, the takeaway is that a kitten's total course usually costs more than a snapshot of week one would suggest.

The course length varies. The classic course is 84 days, but research is now studying shorter courses of around 42 days for some cats, and your vet's plan follows the current guidance for your cat's case (Taylor et al., 2025). A shorter course, where appropriate, costs less.

Add those together and you can see why "how much is FIP treatment" honestly has no one answer. It is weight times dose times duration, and all three vary.

When you budget, separate two things in your mind, because they are billed differently.

The first is the medicine itself: the daily oral GS-441524 tablets or liquid, or the injectable remdesivir if your cat starts on injections. This is usually the largest part of the bill, and it is the part that scales with weight and duration.

The second is everything around the medicine: the initial workup to reach the diagnosis, consultations, and the recheck bloodwork your vet runs along the way to make sure treatment is working (Thayer et al., 2022). These are real and necessary costs, and they are easy to forget when you are focused on the drug price. When you ask your vet for an estimate, ask for both parts, so the monitoring does not arrive as a surprise on top.

Here I have to be careful with you, because being vague would be unhelpful and inventing a precise figure would be worse.

What is documented is that FIP treatment in the UK is genuinely expensive, though prices fell meaningfully in 2023 (Taylor et al., 2024). Real UK cases from the earlier, more expensive period ran into several thousand pounds in total once diagnostics, hospitalisation and the full drug course were counted, with published examples around the £5,000 to £6,000 mark before the 2023 price reductions (FIP Cats UK, 2023). Prices have come down since, so a straightforward case today may cost less than those earlier figures, but it is still a substantial sum, commonly running into the low thousands of pounds for a full course once monitoring is included.

I am not going to pin a single number to that, because it would be out of date almost as soon as it was written and because your cat's number depends on the factors above. What I can tell you honestly is the shape: it is a serious expense, usually in the thousands, driven mostly by your cat's weight and the length of the course, and your vet can turn that shape into a real figure for your specific cat in one conversation.

You may read that injectable remdesivir and oral GS-441524 differ in price. Which works out cheaper for your cat depends on the case and the current pricing, and it is genuinely a clinical decision, not a shopping one. Some cats start on injections because they are too unwell for tablets, then move to oral. Others take tablets the whole way. Let your vet choose the form on clinical grounds and cost together, rather than trying to pick the cheaper option yourself, because the wrong choice for a very sick cat is no saving at all. We cover the clinical side in the legal UK route.

This is the part I most want you to read, because if the figure has just landed on you like a stone, it can feel like the conversation is over. It is not. There are real options, and needing them is not a moral failing. Cost genuinely is a barrier for some families, and that says nothing about how much you love your cat.

Check your insurance first. If your cat is insured, the medicine and monitoring may be claimable, which can change the picture entirely. The rules around cascade and unlicensed medicines vary between insurers, so read does pet insurance cover FIP antivirals and then ring your insurer before you commit.

Have the frank cost conversation with your vet. Tell them plainly what you can manage. Vets deal with this constantly and would far rather have the honest conversation than lose a treatable cat to an unspoken budget. Some practices can reduce standard mark-ups on the medicine, spread the cost, or stage payments. The current UK guidance itself acknowledges cost as a real barrier and discusses ways to make treatment more affordable within the legal route (Taylor et al., 2025).

Ask about cost-conscious legal options. For owners facing financial limits, vets can consider approaches such as using oral GS-441524 for the whole course rather than starting with the more expensive injectable, and in some cases adding or switching to other prescribable antiviral options as an adjunct, all decided and monitored by your vet (Taylor et al., 2025). These are things to raise with your vet, not to arrange yourself.

Charities and payment help. Depending on your circumstances, some veterinary charities and hardship schemes may be able to help. Ask your practice what exists locally.

One thing I will say plainly, because you may find it whispered online: the unlicensed black-market route is not the affordable answer. It carries real risks to your cat and none of the safety net of a prescribed, monitored course, and we explain why honestly in the black market question. Cost pressure is exactly the moment that route looks tempting, and exactly the moment it is most worth talking to your vet instead.

Three concrete steps, in order. Check your policy, using our insurance guide to know what to ask. Have the straight cost conversation with your vet, and ask for an estimate that separates medicine from monitoring. And understand that for a growing kitten the dose, and so the cost, will climb through the course, which is expected and is explained in weigh weekly, re-dose weekly.

The number is frightening. It is also, for many families, more workable once insurance, an honest vet conversation and the right form of treatment are all in the picture. Do not let the first, worst figure you see be the one that decides this before you have had that conversation.