FIP Blood Test Results Explained: What Your Cat's Lab Work Is Telling You During Treatment

You ordered the blood work. You waited. And now the results are in front of you, and nothing looks right. Your cat has been on treatment for three weeks. They are eating again — properly, not just sniffing and walking away. Their energy is coming back. You have been weighing them every few days and the number is slowly climbing. Every sign you can see with your eyes says something is improving.

Then you open the lab report and the numbers tell a completely different story.

Globulins: still very high. ALT: has gone up since the last test. Lymphocytes: flagged. You open WhatsApp and type out a message to the CureFIP GCC team at midnight because you cannot wait until morning.

FIP Blood Test Results During Treatment Explained

Here is what you need to know: in most cases, those numbers are not telling you that your cat is getting worse. They are telling you exactly what happens inside the body of a cat responding normally to GS-441524 therapy. The blood work during active FIP treatment is frequently alarming to read — and frequently misread, even by veterinarians who have limited experience with FIP cases in the Gulf region.

This article breaks down every key parameter, explains what it does during treatment, and tells you clearly when a value is expected versus when it genuinely needs immediate attention.

Why Blood Tests Are the Most Important Tool You Have Right Now

Feline Infectious Peritonitis (FIP) is caused by a dangerous mutation of the feline coronavirus (FCoV) — a virus that many cats carry quietly without becoming ill. When that mutation occurs, the result is a disease that attacks multiple organ systems simultaneously, triggering sustained and severe inflammation throughout the body.

GS-441524 works by blocking the virus from replicating inside infected cells. But suppressing a virus that has been active for days or weeks does not mean the body immediately heals. The inflammation, the protein imbalances, the immune system changes — all of these take time to reverse. Blood tests let you track that reversal objectively, at points when what you observe externally may not yet match what is happening internally.

In the GCC, where access to specialist veterinary care can vary significantly between cities, and where some diagnostic tools such as PCR testing are not always available or affordable, blood panels become even more critical. They are frequently the clearest window your veterinarian has into whether the treatment is working.

Blood work during FIP treatment does three things:

• Confirms that the disease is actually retreating — inflammatory markers falling, protein fractions rebalancing

• Flags early side effects — particularly on the liver and kidneys, before any external symptoms appear

• Guides dosing decisions — if the response is slower than expected, the panel gives your treatment team the information they need to adjust

The standard monitoring schedule used by CureFIP GCC follows the same protocol that has been validated in clinical research: a baseline panel before treatment begins, repeat panels at weeks 4 and 8 of the 84-day course, and a final panel at day 84. After treatment ends, the 12-week post-treatment observation period requires additional blood checks at weeks 4, 8, and 12.

No single result tells the whole story. What matters is the direction each value moves across multiple draws over time.

The Key Parameters, Explained One by One

Globulins

What they are: Globulins are immune proteins produced in response to infection. In cats with active Feline Infectious Peritonitis (FIP), globulin levels are almost always dramatically elevated — often between 50 and 90 g/L — because the immune system has been fighting a sustained systemic battle.

What to expect during treatment: Globulins are consistently the last parameter to normalize. It is completely normal for them to remain elevated at the week-4 and week-8 checks, even when the cat is visibly improving across every clinical sign that matters. Do not judge treatment progress by the globulin number alone. Judge it by which direction that number is heading.

What to watch for: Globulins that keep rising after week 8 — while the cat is also showing clinical signs of deterioration — may indicate that the current dose is not achieving adequate viral suppression. This is the conversation to have with the CureFIP GCC team, not a reason to stop treatment unilaterally.

Albumin-to-Globulin Ratio (A:G Ratio)

What it is: The A:G ratio compares albumin — a structural protein made by the liver — to total globulins. In healthy cats, this sits above 0.8. In cats with active Feline Infectious Peritonitis (FIP), it typically falls below 0.5, sometimes as low as 0.3 or lower.

What to expect during treatment: A rising A:G ratio is one of the earliest and most reliable indicators that GS-441524 is working. As globulins begin to fall and albumin begins to recover, this ratio climbs back toward the normal range. Seeing improvement in the A:G ratio at the week-4 draw — even when individual values are still outside normal limits — is one of the clearest positive signals available.

How to read it alongside individual values: A cat whose globulins dropped from 70 g/L to 53 g/L while albumin climbed from 14 g/L to 20 g/L is responding well to treatment — even though neither number is in the healthy reference range yet. The A:G ratio captures that progress. Individual values alone can mislead; the ratio puts them in context.

ALT (Alanine Aminotransferase)

What it is: ALT is a liver enzyme that rises when hepatic cells are stressed or damaged. Elevated ALT in FIP cats can come from the disease itself, or from GS-441524 — which is documented as a cause of moderate, generally temporary ALT elevation in a portion of treated cats.

What to expect during treatment: A moderate ALT rise in the first four to eight weeks of GS-441524 therapy is a well-documented finding. It is not a sign of liver failure. It is not a sign the treatment should stop.

When to act: An ALT that climbs to more than three to five times the upper limit of the reference range, or one that keeps rising after week 8, deserves a closer look. If your cat also develops jaundice — yellow coloring of the gums, the whites of the eyes, or the inner surface of the ears — this is a more urgent finding that requires same-day veterinary assessment or immediate contact with the CureFIP GCC support team.

Never stop treatment based on ALT alone without speaking to a treatment professional first. Premature discontinuation dramatically increases relapse risk — in the vast majority of cases, that risk is far greater than the risk posed by a moderate, monitored enzyme elevation.

ALP (Alkaline Phosphatase)

What it is: ALP is another liver-associated enzyme, frequently elevated alongside ALT during Feline Infectious Peritonitis (FIP) treatment.

What to expect: Mildly elevated ALP during the treatment course is common and typically resolves on its own during or after treatment. Persistently elevated ALP after the cat has been confirmed in remission warrants specific follow-up with a veterinarian.

SDMA and Creatinine (Kidney Function)

What they are: SDMA (symmetric dimethylarginine) and creatinine measure how well the kidneys are filtering waste from the blood. SDMA is a more sensitive early indicator — it can detect reduced kidney function before creatinine rises.

What to expect during treatment: Some cats show transient SDMA elevations during GS-441524 therapy. This does not automatically mean kidney damage — GS-441524 is eliminated through the kidneys, and certain functional shifts can occur without causing lasting harm.

When to act: Rising SDMA combined with elevated creatinine, dilute urine, or noticeably increased water consumption requires veterinary evaluation. Cats who entered treatment with pre-existing kidney disease need more frequent renal monitoring across the full 84 days.

A note for GCC cat parents: In the Gulf's heat, cats already tend to concentrate their urine less than cats in cooler climates. Ensure your cat has constant access to cool, fresh water throughout the treatment period, and mention any changes in drinking or urination habits when you send updates to the CureFIP GCC team.

Complete Blood Count (CBC): White Cells and Differential

What it is: The total white blood cell count and the breakdown of individual cell populations — neutrophils, lymphocytes, eosinophils, monocytes.

What to expect during treatment:

• Lymphocytosis (elevated lymphocytes) has been reported during GS-441524 treatment and is not clinically significant when seen in isolation

• Eosinophilia (elevated eosinophils) is documented as a transient finding and does not by itself indicate parasites or allergic disease, unless accompanied by other signs

• Neutrophilia (elevated neutrophils) early in treatment reflects the active systemic inflammation from Feline Infectious Peritonitis (FIP) itself — this should gradually fall as treatment takes effect

A CBC trending toward the reference range between weeks 4 and 8 is a reassuring sign. Persistent or worsening neutrophilia — particularly if the cat is also developing a fever or going off food — may point to a secondary bacterial infection or insufficient viral control.

Hematocrit (PCV) and Red Blood Cells

What it is: The proportion of red blood cells in circulation. Many cats are anemic at the time of FIP diagnosis due to immune-mediated destruction of red blood cells and suppression of the bone marrow.

What to expect: Anemia improves progressively as viral load decreases and the immune response stabilizes. Normalization in the first two to four weeks is not realistic. Cats still severely anemic at week 8 may benefit from supportive measures discussed with the treating veterinarian.

Total Protein and Fibrinogen

What they are: Total protein is albumin plus globulins. Fibrinogen is an acute-phase protein that spikes significantly with systemic inflammation.

What to expect: Total protein normalizes as albumin climbs and globulins fall. Very high baseline values — above 90–100 g/L — are consistent with active Feline Infectious Peritonitis (FIP). A sustained downward trend across the 84-day course is the indicator that matters.

How to Read the Blood Work at Each Stage of Treatment

Before Treatment Starts (Baseline Panel)

This panel documents the severity of the disease at the starting point. Expect elevated globulins, depressed albumin, low A:G ratio, possible anemia, and disrupted inflammatory markers. This is not a comparison to a healthy cat's reference range — it is the zero point against which every subsequent result will be measured.

Week 4 (Day 28)

Cats responding to treatment typically show at this draw:

• A:G ratio improving, even if individual values remain outside reference limits

• Globulins lower than baseline (may still be substantially elevated)

• CBC moving toward normal

• Partial improvement in anemia

• ALT possibly elevated but stable, not climbing

If globulins have not moved and clinical signs have not improved, contact the CureFIP GCC team immediately to discuss whether the dose may need adjustment. Verify the current dosing against the cat's actual body weight using the CureFIP GCC Dosage Calculator before any conclusions about treatment failure are reached.

Week 8 (Day 56)

A well-responding cat at week 8 should show values clearly approaching the reference range. Globulins should be measurably lower than at week 4. ALT and ALP, if elevated, should be stable or declining. Albumin should show a clear recovery trend.

If values at week 8 are moving in the wrong direction, do not adjust the treatment yourself. Reach out to the CureFIP GCC support team via WhatsApp with the full panel results.

Day 84 (End of Treatment)

The goal at day 84 is clinical remission supported by a clear laboratory trend toward normal — not necessarily perfect numbers across every parameter. Globulins in particular may still be slightly elevated. The criteria for ending the 84-day course are:

• Clinical remission: normal appetite, stable or increasing weight, normal energy levels, normal body temperature

• A:G ratio at or approaching the reference range

• No active effusions

• No other markers of ongoing active disease

For a complete overview of what clinical milestones to expect at each phase of the treatment journey, see the GS-441524 Treatment Timeline for FIP in Cats.

Post-Treatment Observation: Weeks 4, 8, and 12 After Day 84

The 12-week observation period is not optional — it is a structured phase with its own blood work requirements. At each of the three draws, values should continue normalizing. Any parameter that deteriorates after treatment ends — particularly globulins rising again, or albumin falling — must be reported to the CureFIP GCC team immediately. This pattern is one of the primary indicators of relapse, and early action matters significantly for outcomes.

The Most Common Misreads — and the Truth Behind Them

"ALT has gone up. I need to stop the medication." In most cases, no. Moderate ALT elevation during GS-441524 therapy is expected and generally reversible. Stopping treatment prematurely is one of the most preventable causes of relapse in FIP cases across the GCC. Do not make this decision without speaking to your treatment team.

"Everything looks almost normal at week 4. Can we stop early?" No. Normalized lab values do not mean the virus has been cleared. The 84-day protocol exists because feline coronavirus can persist inside macrophages — immune cells — even when blood markers improve. Stopping early is the most common reason cats relapse unnecessarily.

"The results haven't improved at week 4. The treatment isn't working." Clinical improvement — appetite returning, fever resolving, energy increasing — almost always precedes laboratory normalization by two to four weeks. If your cat looks and behaves better but the blood work is lagging, the treatment is very likely working. Evaluate both together before drawing conclusions.

"Globulins are still high at week 8. That must mean something is wrong." Globulins are the last parameter to normalize in virtually every successfully treated FIP case. Many cats still show elevated globulins at week 8 while on a clear path to full remission. A consistent downward trend — even a slow one — is the signal you are looking for.

FAQ: FIP Blood Tests During Treatment

What blood tests should be done during FIP treatment?

A complete chemistry panel — including total protein, albumin, globulins, ALT, ALP, creatinine, SDMA, and glucose — plus a full blood count (CBC) with differential. The A:G ratio is calculated from albumin and globulins. Minimum recommended testing points: baseline before starting, week 4, week 8, and day 84 at end of treatment.

What do high globulins mean in a cat with FIP?

Elevated globulins reflect sustained immune system activation caused by the feline coronavirus infection. This is expected during the early and middle phases of GS-441524 treatment. A consistently declining trend — even when absolute values remain above the reference range — is a positive indicator of treatment response.

Is it normal for ALT to rise during GS-441524 treatment?

Yes. Moderate ALT elevation is a documented and generally transient side effect of GS-441524 therapy. It does not automatically indicate liver damage or treatment failure. Regular monitoring is essential, and any marked or progressive rise should be discussed with the CureFIP GCC team before treatment is modified.

What is the A:G ratio and why does it matter for FIP?

The albumin-to-globulin ratio (A:G ratio) compares two protein fractions in the blood. In healthy cats it sits above 0.8. In cats with active FIP it typically falls below 0.5. A rising A:G ratio during treatment is one of the earliest and most reliable signs that GS-441524 is working.

How often should blood tests be done during the 84-day FIP treatment?

Minimum schedule: baseline before starting, week 4, week 8, day 84. After treatment, blood checks at weeks 4, 8, and 12 of the observation period confirm sustained remission.

Can blood work look normal and the cat still relapse?

Yes. Lab values can normalize before the virus is fully eliminated. This is a core reason why the complete 84-day treatment course and the full 12-week observation period are both necessary — regardless of how good the blood work looks at any given point.

My cat's results are worse at week 4. What do I do?

Contact the CureFIP GCC team immediately via WhatsApp with the full panel results. Deteriorating values at week 4 may indicate the dose is too low for your cat's current weight, a product quality issue, or a form of FIP requiring a higher-dose or adjusted protocol. Do not change the dose or stop treatment on your own.

What happens to SDMA during FIP treatment?

Transient SDMA elevation has been documented in some cats during GS-441524 therapy. It does not necessarily indicate permanent kidney damage. Cats with pre-existing kidney disease require more frequent renal monitoring. SDMA that remains elevated or continues rising after treatment ends warrants further investigation with a veterinarian.

Where can I get blood tests done for my cat in the GCC?

Most veterinary clinics in Dubai, Abu Dhabi, Riyadh, Jeddah, Doha, Muscat, Kuwait City, and Manama can run a full chemistry panel and CBC in-house or via referral laboratory. The CureFIP GCC team can help you identify what specific parameters to request, and how to send the results for review via WhatsApp.

What to Do With Every Result You Receive

Keep every blood panel. Photograph the report the day it arrives. Build a simple table — even in your phone notes — with the date and the key values: globulins, albumin, A:G ratio, ALT, hematocrit. What you are building is a trend line, and trend lines are what tell the real story.

When you share results with the CureFIP GCC team, send the complete panel — not just the values that concern you. Context is everything in interpreting FIP lab work, and the team needs the full picture to give you accurate guidance.

If warning signs reappear after treatment ends — returning fever, reduced appetite, weight loss, abdominal swelling, or any neurological changes — do not wait for the next scheduled appointment. Contact us immediately. Our Relapse Programme is designed for exactly this situation, offering a structured path back into treatment quickly and with the right protocol for your cat's specific situation.

CureFIP GCC supports cat parents across the UAE, Saudi Arabia, Bahrain, Qatar, Kuwait, and Oman with pharmaceutical-grade GS-441524, dosing guidance, and treatment monitoring. Reach our team directly via WhatsApp or email — we are here throughout the entire journey, from first diagnosis to confirmed recovery.