What To Do When Your Cat Shows FIP Symptoms: A Step-by-Step Action Plan

Seeing your cat experience sudden health changes is one of the most distressing moments a pet owner can face. When Feline Infectious Peritonitis (FIP) is suspected, the instinct to panic is understandable — but quick, informed action is what makes the difference between a cat that recovers and one that does not.

FIP is caused by a mutation of the feline coronavirus (FCoV). It used to be considered fatal. Today, with GS-441524 antiviral treatment, the vast majority of cats diagnosed with FIP can achieve full remission — but only when treatment starts early and the full 84-day protocol is completed correctly.

This guide tells you exactly what to do, step by step.

Symptoms of FIP in Cats

FIP presents differently depending on which form your cat has. The symptoms below are the most commonly reported before diagnosis. If your cat is showing three or more of these signs, contact a veterinarian familiar with FIP immediately.

General symptoms (all forms of FIP):

  • Persistent fever above 39.5°C that does not respond to antibiotics
  • Lethargy and unusual sleepiness
  • Loss of appetite or refusing food
  • Significant weight loss, often visible along the spine
  • Vomiting or diarrhoea
  • Rough, dull coat and reduced grooming
  • Jaundice (yellowing of the gums or eyes)
  • Anaemia (pale gums)

Form-specific symptoms:

  • Enlarged, fluid-filled abdomen (wet FIP)
  • Difficulty breathing or panting (wet FIP with chest fluid)
  • Eye colour changes, cloudiness, or unequal pupils (ocular FIP)
  • Wobbly gait, seizures, or behaviour changes (neurological FIP)

For a detailed breakdown of all 12 early warning signs and the four forms of FIP, read our complete FIP symptoms guide.

Step 1: See a Veterinarian Immediately

The first and most important step is an accurate diagnosis. Do not start any treatment before a vet has examined your cat.

Ask your vet specifically about FIP testing. A confident FIP diagnosis combines:

  • Complete Blood Count (CBC) — looking for anaemia, low lymphocytes, and elevated white cells
  • Albumin-to-Globulin (A:G) ratio — below 0.6 is highly suggestive; below 0.4 is strongly indicative of FIP
  • Rivalta test — performed on any abdominal or chest fluid; ~91% sensitivity for FIP
  • PCR testing — detects feline coronavirus genetic material
  • Ultrasound or X-ray — to identify fluid pockets or organ granulomas

No single test is definitive on its own, but combining these tools reaches diagnostic confidence above 90%. For a full explanation of what each blood marker means, read our guide to reading your cat’s blood work during FIP treatment.

Step 2: Confirm the Form of FIP and Calculate the Correct Dose

Once FIP is confirmed, your vet identifies which form your cat has. The correct GS-441524 dose depends on both the form and your cat’s weight. Getting this right from day one is critical — under-dosing is the most common cause of treatment failure.

FIP Form GS-441524 Injectable Dose Frequency Duration
Wet (Effusive) 6 mg/kg Once daily, subcutaneous 84 days
Dry (Non-effusive) 8 mg/kg Once daily, subcutaneous 84 days
Ocular 10 mg/kg Once daily, subcutaneous 84 days
Neurological 10 mg/kg Once daily, subcutaneous 84 days

Dosing follows Pedersen et al., UC Davis (PMC6435921). Your veterinarian confirms form and weight before the first injection.

Step 3: Obtain GS-441524 and Start Treatment Immediately

FIP progresses quickly. Once the diagnosis is confirmed and the dose is calculated, start treatment as soon as possible. Every day matters.

FIP CURE Plus supplies GS-441524 in two concentrations to match your cat’s form and dose:

All pricing is listed openly in AED. View the full FIP CURE Plus product range.

GS-441524 injectable monotherapy carries a 92% success rate documented by UC Davis (Pedersen, 2019). The key is starting at the correct dose and completing the full 84 days without interruption.

Step 4: Provide Extra Care and a Supportive Environment

During the 84-day protocol, your cat’s body is fighting hard. Supporting recovery through nutrition and environment makes a real difference:

  • Offer high-quality, palatable food — wet food is often easier for sick cats to eat
  • Keep your cat in a calm, warm, low-stress environment
  • Ensure fresh water is always available
  • Avoid unnecessary supplements unless specifically recommended by your vet
  • Do not change the GS-441524 dose or schedule without consulting your vet

For detailed feeding guidance during FIP treatment, read our complete FIP diet guide.

Step 5: Monitor Progress With Regular Blood Tests

Blood work is not just for diagnosis — it is how you confirm GS-441524 is working. Your vet should run a full panel at each of these points:

  • Day 0 (before starting): Full baseline including CBC, biochemistry, A:G ratio, and bilirubin
  • Day 30: First progress check — most cats show clear improvement by this point
  • Day 60: Continued progress assessment
  • Day 84 (end of treatment): Final panel before entering the 12-week observation period
  • Week 12 post-treatment: Confirmation of sustained remission

Key markers to track: A:G ratio (rising toward normal), globulin levels (falling), albumin (rising), RBC and platelet counts (recovering), and ALT/bilirubin (normalising). For a full explanation of what each result means, read our blood work guide for FIP cat owners.

Step 6: Complete the Full 84 Days — No Exceptions

This is the step most often cut short — and the most common cause of relapse. Even if your cat looks and feels completely normal at day 40 or 50, stopping early allows the virus to rebound.

The 84-day protocol is followed by a 12-week observation period. Only after both phases are completed without symptom recurrence is a cat considered in full remission.

Read our FIP relapse guide to understand the signs of relapse, what causes it, and what to do if it happens.

Signs Your Cat Is Responding to GS-441524 Treatment

Most cats on the correct dose show visible improvement within the first 7 to 14 days:

  • Fever resolves or reduces significantly
  • Appetite returns
  • Energy and playfulness increase
  • Abdominal fluid reduces (wet FIP)
  • Weight stabilises and begins to increase
  • Blood work markers improve at the 30-day check

For a full picture of what recovery looks like over time, read our guide on how long cats can live with FIP and what recovery looks like.

Frequently Asked Questions

How quickly should I start GS-441524 after an FIP diagnosis?
As soon as possible. FIP progresses rapidly, and every day without treatment allows the virus to replicate further. Once your vet confirms the diagnosis and calculates the dose, start treatment immediately.

What is the correct GS-441524 dose for my cat?
It depends on your cat’s form of FIP and weight. Wet FIP: 6 mg/kg. Dry FIP: 8 mg/kg. Ocular and neurological FIP: 10 mg/kg. All doses are once daily subcutaneous injections for 84 days. Your vet confirms this before the first injection.

What if my cat refuses to eat during treatment?
Appetite loss is common in the early days of FIP. Offer warm, aromatic wet food and try hand-feeding if needed. Read our FIP diet guide for practical strategies.

Can FIP come back after treatment?
Relapse is uncommon when the full 84-day protocol is completed correctly. The most common cause of relapse is stopping treatment early. Read our FIP relapse guide for full details.

How do I know if the treatment is working?
Clinical signs (appetite, energy, fever) typically improve within 7–14 days. Blood work at day 30 confirms whether the A:G ratio and other markers are moving in the right direction. Read our blood work guide for what to look for.

Conclusion

An FIP diagnosis is no longer a death sentence. With GS-441524 treatment started early, the correct dose maintained for 84 days, and regular blood work monitoring, the vast majority of cats achieve full remission.

The steps are clear: get a confirmed diagnosis, calculate the correct dose, start treatment immediately, support your cat through nutrition and care, monitor with blood work every 30 days, and complete the full protocol without stopping early.

If you have questions about which GS-441524 product is right for your cat’s weight and FIP form, the FIP CURE Plus team is available in English and Arabic at info@fipcureplus.com.

View the FIP CURE Plus GS-441524 injectable range →

FIP CURE Plus — transparent, evidence-based GS-441524 treatment for cats across the Gulf.

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