The 84 Day FIP Treatment Protocol: Week by Week

The standard Feline Infectious Peritonitis (FIP) treatment protocol runs 84 days (12 weeks) of daily GS-441524 antiviral therapy, given under veterinary supervision. GS-441524 is the antiviral at the core of modern FIP treatment, and the daily dose is set by which of the four forms of FIP your cat has. Most cats show early improvement in the first one to two weeks, then move through steady recovery toward the end of the course.

This guide walks you through what each phase of the 84 day protocol looks like, from the first injection to the final bloodwork, so you know what to watch for and when.

A cat resting comfortably at home.

What is the 84 day FIP treatment protocol?

The 84 day Feline Infectious Peritonitis (FIP) treatment protocol is a 12-week course of daily GS-441524, the proven antiviral at the center of FIP care. The schedule is one subcutaneous injection per day, 7 days a week, for 84 days (12 weeks), with the dose matched to your cat's form of FIP and body weight.

GS-441524 works by stopping the virus from replicating, which gives your cat's body the room it needs to recover. Across the whole treatment network, more than 140,000 cats have been treated, saved, or helped since 2019, including cats treated with GS-441524.

The evidence behind this approach is strong. In the Ansari Mood et al. 2025 cohort of 629 cats on GS-441524 for at least 12 weeks, survival reached 94.12%, meaning more than 9 out of 10 cats survived (Ansari Mood et al. 2025). Results vary from cat to cat, and a success rate is a statistic, not a promise.

If you are still learning the basics, our plain English guide to FIP in cats is a helpful place to start before you begin treatment.

What are the four forms of FIP and how do they change dosing?

Feline Infectious Peritonitis (FIP) takes four distinct forms, and each one shapes the daily GS-441524 dose. The four forms are wet (effusive), dry (non-effusive), ocular, and neurological, and the dose rises as the virus reaches harder-to-treat areas like the eyes and nervous system.

Wet (effusive) FIP: 6 mg/kg

Wet FIP, also called effusive FIP, is marked by fluid buildup in the abdomen or chest, which can cause a swollen belly or labored breathing. For wet FIP, the GS-441524 dose is 6 mg/kg once daily. Many caregivers notice the fluid starting to reduce within the first week or two of treatment.

Dry (non-effusive) FIP: 8 mg/kg

Dry FIP, also called non-effusive FIP, produces inflammatory lesions in the organs without the obvious fluid buildup, so it can be harder to spot early. For dry FIP, the GS-441524 dose is 8 mg/kg once daily. Our FIP symptoms checklist can help you recognize the early signs.

Ocular FIP: 10 mg/kg

Ocular FIP affects the eyes, with signs like iris color change, cloudiness, inflammation inside the eye (uveitis), and vision loss from ocular lesions. For ocular FIP, the GS-441524 dose is 10 mg/kg once daily, because a higher dose is needed to reach eye tissue effectively.

Neurological FIP: 10 mg/kg

Neurological FIP affects the nervous system, with signs such as seizures, head tilt, loss of balance, paralysis, and disorientation. For neurological FIP, the GS-441524 dose is 10 mg/kg once daily, since the antiviral must cross into the central nervous system to work.

Dosing by form at a glance

The 6/8/10 mg/kg standard is consistent with current clinical practice. Gokalsing et al. 2025 found the best outcomes fall within the 5 to 10 mg/kg once-daily range, adjusted for FIP type and neurological or ocular signs. Your veterinarian confirms the exact dose for your cat's weight and form.

What happens week by week during FIP treatment?

Most cats move through three broad recovery stages during the 84 day FIP treatment protocol: early response, steady improvement, and consolidation. Here is what each stage typically looks like.

1. Weeks 1 to 2 (early response). This is often the most dramatic phase. Appetite frequently returns, fever drops, and energy begins to pick up. In wet FIP, fluid often starts to reabsorb. This is also when your cat's body adjusts to daily injections, so gentle handling and a calm routine help a great deal.

1. Weeks 3 to 6 (steady improvement). Weight starts to climb back, coat quality improves, and playfulness returns. Neurological and ocular signs usually improve more gradually than wet FIP signs, so patience matters here. Many cats look close to normal by the end of this window, but the virus is not finished, so the daily schedule continues without gaps.

1. Weeks 7 to 12 (consolidation). Your cat often looks and acts healthy, eating and playing again. This final stretch is about finishing the full course to lower the chance of relapse. Completing all 84 days under veterinary supervision is one of the most important things you can do for a lasting result.

Consistency is everything. Missing doses or stopping early can undo progress, which is why the protocol is a fixed daily schedule for the full 12 weeks.

What bloodwork milestones should you expect?

Bloodwork is how you and your veterinarian confirm that the treatment is working beneath the surface, not just in your cat's behavior. Your veterinarian sets the exact testing schedule, but most protocols include bloodwork before treatment starts and at regular checkpoints through the 84 days.

Common markers your veterinarian follows include:

• Total protein, albumin, and globulin, which often normalize as inflammation falls.

• The albumin-to-globulin (A:G) ratio, which typically rises toward a healthier range.

• Packed cell volume (PCV) or hematocrit, which improves as anemia resolves.

• White blood cell counts, which tend to settle as the body recovers.

These milestones give you real, measurable proof of progress. When bloodwork and behavior both point in the right direction near day 84, your veterinarian helps you decide whether your cat is ready to finish the course and enter observation.

How much does the FIP treatment protocol cost?

The cost of the FIP treatment protocol depends on the GS-441524 concentration your veterinarian selects and your cat's weight, because a heavier cat and a higher-dose form need more milligrams per day. Here are the GS-441524 injectable options and prices exactly as listed in our catalog.

If your cat may benefit from added B12 support, there are also combination options: GS-441524 Antiviral with Vitamin B12 | 20mg/ml at $75.00 (20 mg/ml + B12 50mcg/ml) and GS-441524 Antiviral with Vitamin B12 | 30mg/ml at $95.00 (30 mg/ml + B12 50mcg/ml). These use the same dosing and indications as the standard injectable, with B12 as an addition rather than a separate antiviral.

We are upfront about cost because planning the full 12 weeks ahead of time helps you finish the course. The only guarantee we offer is simple: you can cancel any time before your order ships for a full refund.

Can you switch to oral capsules during the protocol?

Yes, many caregivers transition to oral capsules after 2 to 4 weeks of GS-441524 injections, or once the cat is stable, which is common practice including in ocular and neurological cases. The dual antiviral option is Cure FIP™ Oral Capsules at $129.00, which combine GS-441524 + EIDD-1931 in one capsule.

The key advantage is simplicity: one capsule a day for your cat's weight class, with no mg calculation and no counting capsules. One pill covers one weight class.

The recommended course for the dual capsule is 12 weeks. In our own data from about 46 treated cats on the dual antiviral GS-441524 + EIDD-1931, 78.3% reached remission, meaning about 8 out of 10 cats on the dual antiviral reached remission.

The dual capsule is not for cats with vomiting or diarrhea, cats under 1 year old with wet (effusive) FIP, cats that cannot eat or defecate normally, or pregnant, nursing, or breeding cats, because it contains EIDD-1931. Your veterinarian decides if and when the switch is right for your cat.

FAQ

How long is the FIP treatment protocol?

The standard Feline Infectious Peritonitis (FIP) treatment protocol is 84 days (12 weeks) of daily GS-441524, given as one subcutaneous injection per day, 7 days a week. Finishing the full course under veterinary supervision is important for a lasting result.

When will I see my cat start to improve on FIP treatment?

Many cats with Feline Infectious Peritonitis (FIP) show early improvement in appetite, energy, and fever within the first one to two weeks of GS-441524 treatment. Neurological and ocular signs often improve more gradually, so steady patience through the full 84 days matters.

Does the GS-441524 dose change for different forms of FIP?

Yes. For Feline Infectious Peritonitis (FIP), the daily GS-441524 dose is 6 mg/kg for wet (effusive), 8 mg/kg for dry (non-effusive), 10 mg/kg for ocular, and 10 mg/kg for neurological FIP. Your veterinarian confirms the exact dose for your cat's weight and form.

What does the evidence show about GS-441524 success rates?

In Pedersen et al. 2019, 24 of the 26 cats that completed injectable GS-441524 treatment remained healthy, a 92% success rate, meaning more than 9 out of 10 cats that completed injectable GS-441524 treatment stayed healthy. A systematic review by Gokalsing et al. 2025 across 11 studies and 650 cats reported 84.6% overall success, meaning more than 8 out of 10 cats were treated successfully. Each cat is different, and these figures are statistics, not promises.

Can I give oral capsules instead of injections?

Many caregivers switch to Cure FIP™ Oral Capsules after 2 to 4 weeks of GS-441524 injections or once the cat is stable, offering one capsule a day for the cat's weight class. This option is not for pregnant, nursing, or breeding cats, or cats that cannot eat or defecate normally, so your veterinarian guides the timing.

Starting the 84 day protocol is a big step, and you do not have to navigate it alone. Learn more about the GS-441524 options and talk through the right plan with our team or your own veterinarian by exploring FIP treatment at CureFIP. With the right protocol and steady daily care, many cats go back to eating, playing, and simply being themselves.