Key takeaway: The cost of treating Feline Infectious Peritonitis (FIP) in the UK depends mainly on two things: your cat's body weight, which sets how many capsules per dose, and the length of the course, which is usually 60 days and sometimes longer. There is no single flat price, because a small cat on a standard course needs far less medicine than a large cat on an extended course. Your veterinarian and the storefront pricing together give you the real figure for your cat.
If your cat has just been diagnosed, you are probably scared and scrolling fast. This guide walks you through what actually drives the cost of FIP care, so you can plan calmly and talk to your vet with clear questions.
A cat resting comfortably at home.
What makes FIP treatment cost different for every cat?
FIP treatment cost is set by your cat's weight and the length of the course, not by a single fixed price. Heavier cats need more capsules at each dose, and longer courses use more medicine overall, so two cats with the same diagnosis can have very different totals.
Feline Infectious Peritonitis (FIP) is caused by a mutated form of the common feline coronavirus (FCoV). It appears in four distinct forms: wet (effusive), dry (non-effusive), ocular, and neurological. The form your cat has can change how treatment is structured, which also affects the overall cost.
Because every cat is different, the honest answer to "how much will this cost?" is: it depends on these specific factors. Below, we break each one down so there are no surprises.
How does my cat's weight affect the cost of FIP treatment?
Your cat's weight directly sets how many capsules they take at each dose, so it is one of the biggest cost drivers. FipX, the oral EIDD-1931 option, is dosed at 1 capsule (15 mg) per 2.5 kg (5.5 lb) of body weight, every 12 hours.
Here is how the weight bands work for FipX:
| Cat's weight | Capsules per dose | Schedule |
| Under 2.5 kg (under 5.5 lb) | 1 capsule | Every 12 hours |
| 2.5 to 5 kg (5.5 to 11 lb) | 2 capsules | Every 12 hours |
| Over 5 kg (over 11 lb) | 3 capsules | Every 12 hours |
EIDD-1931 is the active antiviral metabolite of molnupiravir, not the human capsule, and FipX capsules come in a 15 mg strength with 60 capsules per bottle. A larger cat simply moves through more capsules each day, which is why weight matters so much to your final cost.
Your veterinarian should confirm your cat's current weight and the right capsule count before you start, since dosing correctly for weight and condition is what keeps treatment on track.
How long is a course of FIP treatment, and how does that change the price?
A standard FIP course with FipX runs 60 days. Chronic or severe cases may run up to 90 days or longer depending on how your cat responds, and an 84-day course sits comfortably within that range.
Course length is the second major cost driver. A cat who needs the extended timeline will use more medicine than one who completes the standard 60 days, so planning for the possibility of a longer course helps you avoid a budgeting shock midway through.
One important point on cost: chronic under-dosing can actually prolong treatment and raise the total. Getting the dose right for your cat's weight and condition from the start is the most cost-aware thing you can do. For a sense of how these same factors play out in another market, you can compare this with our guide on how FIP treatment is priced for a cat in Australia.
What treatment options are there for FIP in the UK?
FIP care generally uses antiviral medicine, and the main routes are GS-441524 injectables and oral EIDD-1931 capsules (FipX), sometimes used in sequence. Many Pawrents start with a phase of GS-441524 injections and then move to FipX capsules, a common approach that includes ocular and neurological cases.
Here is how the options compare:
| Option | What it is | Commonly used for |
| GS-441524 injectables | Injectable antiviral | Often the starting phase, including ocular and neurological FIP |
| FipX (EIDD-1931 capsules) | Oral antiviral, 15 mg per capsule | Wet, dry, mixed and transitional FIP; continuing after 2 to 4 weeks of injections |
| Dual capsule | One pill per weight class | A convenient oral option your vet can discuss |
For the dual capsule, the appeal is simplicity: one pill per weight class, using the same kg and lb bands above. GS-441524 injectables report a 92% success rate, which many Pawrents find reassuring when weighing the injection phase. Your veterinarian can help you decide which route, or combination, fits your cat's form of FIP and your budget. Our overview of what the evidence shows on FIP treatment choices explains the science behind these options in plain terms.
Why can't I just get an exact price upfront?
An exact FIP treatment price cannot be quoted in advance because it is built from your cat's weight band, the capsule count that follows, and the final course length your vet sets based on response. Those variables are only fully known once your cat is assessed and treatment begins.
The storefront shows current availability and pricing for each product, so that is where you confirm the cost of a bottle. Pairing that figure with your cat's capsule count and expected course length gives you a realistic estimate rather than a guess.
There are no guarantees in medicine, and no treatment can promise a certain outcome. What MolnuFIP does offer is a clear refund policy: you can cancel any time before your order ships for a full refund, which takes some of the pressure off the decision while you plan with your vet.
What else should I budget for during FIP treatment?
Beyond the antiviral medicine itself, budget for veterinary monitoring and supportive care, which are part of responsible FIP treatment. Your vet will want to track your cat's weight, appetite, and bloodwork across the course, and these check-ins carry their own costs.
Keep these supportive-care points in mind:
- Supportive care, such as good nutrition and hydration, helps your cat through treatment.
- Regular veterinary monitoring lets your vet adjust dosing and catch problems early.
- Some products are best started only once your cat is eating and defecating normally, so stabilising your cat first may add early vet costs.
There are also things to avoid during FIP treatment, which can save you money and protect your cat: fluoroquinolone antibiotics, spot-on flea medications, lysine, and immune boosters are all best avoided while your cat is on antiviral therapy. Always clear any extra product with your veterinarian first.
Does the form of FIP change the cost?
Yes, the form of FIP can change how treatment is structured and therefore the cost. Feline Infectious Peritonitis (FIP) has four forms, wet (effusive), dry (non-effusive), ocular, and neurological, and the ocular and neurological forms often involve the injection phase at the start rather than oral capsules alone.
Ocular FIP shows signs such as iris colour change, cloudiness, inflammation inside the eye (uveitis), and vision loss. Neurological FIP shows signs such as seizures, head tilt, loss of balance, paralysis, and disorientation. A colour change in the eye is an ocular sign, not a neurological one.
Because ocular and neurological cases commonly start with GS-441524 injections before moving to FipX, the treatment plan, and the cost, can differ from a straightforward wet or dry case. Your veterinarian will map the right path for your cat's specific form.
How many cats has this kind of treatment helped?
Across the whole network, more than 140,000 cats have been treated since 2019, a figure that includes cats treated with GS-441524. That scale is one reason many UK Pawrents feel more confident starting treatment, even though every cat responds differently and no outcome is ever certain.
Numbers like these are statistics, not promises. They describe experience across many cats, and your own cat's journey will be guided by your vet, your cat's form of FIP, and how they respond to the course.
If you are also comparing where care is delivered, our look at which clinics treat FIP in cats shows the kinds of questions worth asking any veterinary team.
FAQ
How much does FIP treatment cost for a cat in the UK?
The cost of Feline Infectious Peritonitis (FIP) treatment in the UK varies with your cat's weight and course length, so there is no single fixed price. Check current product pricing on the storefront, then confirm your cat's capsule count and expected course length with your veterinarian for a realistic estimate.
How long does a course of FIP treatment last?
A standard FipX course for Feline Infectious Peritonitis (FIP) is 60 days, and chronic or severe cases may run up to 90 days or longer depending on response. An 84-day course falls within that normal range, and your veterinarian sets the final length.
How is FipX dosed by weight?
FipX is dosed at 1 capsule (15 mg) per 2.5 kg (5.5 lb) every 12 hours: 1 capsule for cats under 2.5 kg (under 5.5 lb), 2 for cats 2.5 to 5 kg (5.5 to 11 lb), and 3 for cats over 5 kg (over 11 lb). Your veterinarian should confirm the right count for your cat.
Is there any money-back option if I change my mind?
Yes. You can cancel any time before your order ships for a full refund. This is the only guarantee offered, because there are no guarantees of a medical result.
Can FipX be used for ocular or neurological FIP?
Ocular and neurological Feline Infectious Peritonitis (FIP) are commonly treated starting with GS-441524 injections, then continuing with FipX, rather than oral capsules alone from the outset. Your veterinarian will decide the right starting point for your cat's form.
Facing an FIP diagnosis is frightening, but you do not have to work it out alone. Take a moment to explore the available FIP treatment options and talk with our team, and bring your questions to your own veterinarian, who will guide dosing and monitoring for your cat. Every cat is different, and a calm, well-planned start gives you the clearest path forward.
