How Much Does FIP Treatment Cost for a Cat in the US?

Key takeaway: Feline Infectious Peritonitis (FIP) treatment cost in the US is driven mainly by four things: your cat's body weight, how long treatment runs (often up to about 60 days), which form of the disease is present, and the veterinary monitoring and supportive care around it. There is no single flat price, because a 3 kg kitten and a 6 kg adult cat need very different amounts of antiviral medication over the full course. Here is what the current picture actually looks like, and how to plan for it.

A cat resting comfortably at home.

How much does Feline Infectious Peritonitis (FIP) treatment cost in the US?

The total cost of Feline Infectious Peritonitis (FIP) treatment in the US is not a fixed number, because it scales with your cat's weight and the length of the course. The two biggest cost drivers are the amount of antiviral medication your cat needs each day and how many days of treatment your veterinarian recommends.

On top of the medication, most Pawrents budget for diagnostic testing, follow-up bloodwork, and veterinary visits. These supportive costs are real, and they matter, because monitoring is how you and your veterinarian confirm your cat is actually moving toward remission.

Because prices shift by region, provider, and product, the most reliable way to get a real number is to combine your cat's current weight with a planned treatment length and ask your veterinarian and the MolnuFIP team for a specific estimate.

What makes Feline Infectious Peritonitis (FIP) treatment cost go up or down?

Feline Infectious Peritonitis (FIP) treatment cost goes up or down based on a short list of predictable factors. Understanding them helps you plan instead of guess.

The main cost drivers are:

• Body weight. Dosing is weight based, so a heavier cat uses more medication per day.

• Treatment length. A longer course means more total doses. Many FIP protocols run up to about 60 days under veterinary guidance.

• Disease form. Wet, dry, neurological, and ocular FIP are four separate forms, and they are not managed the same way.

• Monitoring. Bloodwork, imaging, and recheck visits add to the total but protect your cat.

• Supportive care. Fluids, appetite support, and organ support may be needed early on.

If you are still learning how the disease itself behaves, our complete 2026 guide to what FIP is is a useful companion to this cost breakdown.

How does a cat's weight affect Feline Infectious Peritonitis (FIP) treatment cost?

Weight is the single largest driver of Feline Infectious Peritonitis (FIP) treatment cost, because antiviral dosing is calculated per kilogram of body weight. A larger cat simply needs more capsules per dose, which raises the daily and total spend.

MolnuFIP for FIP contains EIDD-1931 at 15 mg per capsule. The general dosing reference is 1 capsule every 12 hours per 2.5 kg of body weight, given for up to 60 days under veterinary guidance.

Here is how the per-dose need scales with weight, using that reference:

Cat weight	Capsules per 12-hour dose	What this means for cost
About 2.5 kg	1 capsule	Lowest daily medication need
About 5 kg	2 capsules	Roughly double the daily medication
Above 5 kg	More capsules, set by your veterinarian	Higher daily and total need

Because every cat is weighed and reassessed during treatment, your veterinarian should confirm the exact number of capsules per dose. Do not adjust dosing on your own.

How long does Feline Infectious Peritonitis (FIP) treatment last, and how does that affect cost?

Feline Infectious Peritonitis (FIP) treatment commonly runs as a full multi-week course, often up to about 60 days under veterinary guidance, and the length directly multiplies the total cost. Two doses per day across that window adds up to a meaningful number of capsules.

This is why stopping early to save money is risky. Studies and clinical experience show that finishing the full prescribed course, then monitoring afterward, gives the best chance of durable remission.

Many Pawrents find it easier to plan when they think in phases: an initial treatment phase, then a post-treatment observation window where your veterinarian confirms your cat is stable. For a broader view of how remission is defined and measured, see our evidence review on whether FIP in cats can be cured.

Why does the active ingredient matter to the Feline Infectious Peritonitis (FIP) cost conversation?

The active ingredient matters to the Feline Infectious Peritonitis (FIP) cost conversation because potency affects how much compound is needed to act on the virus. MolnuFIP for FIP uses EIDD-1931, the active antiviral metabolite of molnupiravir, not the human capsule and not a prodrug.

For context, evidence shows EIDD-1931 is roughly 7.3x more potent than GS-441524, a separate competitor compound often discussed in US FIP communities. GS-441524 is only a comparison compound here, and it is not an ingredient in any MolnuFIP product.

That potency difference is one reason Pawrents compare products carefully rather than by sticker price alone. If you are weighing options, our overview of the best treatment approaches for FIP in cats walks through how to think about it, and if you are specifically researching the GS-441524 route, see our US guide on where to buy legitimate GS-441524.

Does the form of Feline Infectious Peritonitis (FIP) change the cost?

Yes, the form of Feline Infectious Peritonitis (FIP) can change the cost, because the four forms differ in how they present and what supportive care they require. FIP has four distinct forms: wet (effusive), dry (non-effusive), neurological, and ocular.

MolnuFIP for FIP is indicated for wet (effusive) FIP, dry (non-effusive) FIP, and mixed or transitional presentations. It is not recommended for ocular FIP or neurological FIP, so if your cat shows signs of those forms, your veterinarian should guide the plan directly.

Knowing the signs helps you describe them accurately to your vet:

• Ocular FIP signs are eye specific: iris color change, cloudiness, inflammation inside the eye (uveitis), and vision loss from ocular lesions.

• Neurological FIP signs are nervous-system specific: seizures, head tilt, loss of balance, paralysis, and disorientation.

An eye color change is an ocular sign, never a neurological one. Our visual guide to all four forms of FIP can help you match what you are seeing to the right category before your appointment.

What extra costs should you budget for with Feline Infectious Peritonitis (FIP)?

Beyond the antiviral itself, budget for diagnostics and monitoring, because confirming Feline Infectious Peritonitis (FIP) and tracking recovery both require veterinary testing. These are the costs Pawrents most often forget in an early estimate.

Common supporting costs include:

1. Initial diagnosis. Bloodwork, fluid analysis for effusive cases, and sometimes imaging.

2. Baseline labs. Values your veterinarian uses as a starting point.

3. Recheck labs during treatment. To confirm your cat is trending toward remission.

4. Supportive care. Appetite support, fluids, or organ support if your cat is very ill at diagnosis.

5. Post-treatment monitoring. Follow-up checks after the course ends.

Many Pawrents report that early, aggressive supportive care in the first days makes the whole course smoother. Every cat responds differently, so your veterinarian should tailor the monitoring schedule to your cat's condition.

How can you keep Feline Infectious Peritonitis (FIP) treatment affordable without cutting corners?

You can manage Feline Infectious Peritonitis (FIP) treatment cost by planning the full course up front rather than paying piecemeal, and by never shortening the course to save money. Under-treating often leads to relapse, which costs more in the long run.

Practical ways to plan responsibly:

• Get an accurate current weight, since dosing and cost both depend on it.

• Ask your veterinarian for the expected full course length so you can budget the total, not just week one.

• Keep every recheck appointment, because catching a plateau early is cheaper than treating a relapse.

• Ask the MolnuFIP team and your veterinarian for a specific estimate based on your cat's weight and plan.

Important safety note: EIDD-1931 has potential teratogenic effects, so MolnuFIP for FIP must not be used in pregnant, nursing, or breeding cats. Your veterinarian should confirm your cat's status before starting.

MolnuFIP has supported a large community of Pawrents, with 100,000+ cats treated since 2019, and that experience is reflected in how the FIP product line is dosed and monitored. Still, your veterinarian should guide dosing and monitoring throughout treatment.

FAQ

Is there one fixed price for Feline Infectious Peritonitis (FIP) treatment in the US?

No. Feline Infectious Peritonitis (FIP) treatment cost in the US depends on your cat's weight, the length of the course, the form of disease, and monitoring, so a specific estimate should come from your veterinarian and the MolnuFIP team.

Why does a heavier cat cost more to treat for Feline Infectious Peritonitis (FIP)?

A heavier cat costs more because Feline Infectious Peritonitis (FIP) dosing is weight based. MolnuFIP for FIP uses EIDD-1931 at 15 mg per capsule, dosed around 1 capsule every 12 hours per 2.5 kg, so a larger cat needs more capsules per dose and more total capsules over the course.

Does MolnuFIP for FIP contain GS-441524?

No. MolnuFIP for FIP contains EIDD-1931, the active antiviral metabolite of molnupiravir. GS-441524 is only referenced as a separate comparison compound, and evidence shows EIDD-1931 is roughly 7.3x more potent than GS-441524.

Can MolnuFIP for FIP be used for ocular or neurological Feline Infectious Peritonitis (FIP)?

No. MolnuFIP for FIP is indicated for wet, dry, and mixed or transitional Feline Infectious Peritonitis (FIP), and it is not recommended for ocular or neurological forms. If your cat shows eye changes or nervous-system signs, talk with your veterinarian about the right plan.

Will stopping treatment early save money?

Stopping early is not recommended, because an incomplete course raises the risk of relapse, which usually costs more overall. Finishing the full prescribed course, often up to about 60 days under veterinary guidance, gives the best chance of lasting remission.

If your cat has just been diagnosed and you are trying to plan the road ahead, you do not have to do it alone. Learn more about the available FIP treatment options and get a weight-based estimate by talking with the MolnuFIP team, and bring those details to your own veterinarian, who should guide every dosing and monitoring decision for your cat.