High Protein Blood Test in FIP Cats

A high protein blood test in FIP cats is one of the most important laboratory clues veterinarians use when evaluating feline infectious peritonitis, also called FIP. This serious viral disease can affect the abdomen, chest, nervous system, eyes, and internal organs, and bloodwork often reflects widespread inflammation long before the full clinical picture becomes clear. In many cats, the most noticeable pattern is not just a high total protein value, but a combination of increased globulins, reduced albumin, and a low albumin-to-globulin ratio, which together can strongly support suspicion of FIP.

FIP is caused by a mutation of feline coronavirus inside the cat’s body. While many cats are exposed to feline coronavirus, only a small percentage develop FIP. Once the disease becomes active, the immune response can produce marked inflammation, changes in blood protein fractions, fever, poor appetite, weight loss, fluid buildup, and tissue damage. Because the signs can resemble many other illnesses, a high protein blood test in FIP cats is never used alone to confirm the disease, but it is a major part of the diagnostic puzzle.

Why Protein Levels Become Abnormal in FIP Cats

The “protein” measured in routine blood chemistry usually refers to total protein, which includes albumin and globulins. In healthy cats, albumin helps maintain fluid balance and transports substances in the bloodstream, while globulins include antibodies and inflammatory proteins. In FIP, the immune system becomes intensely activated, and globulin production can rise dramatically. At the same time, albumin may fall because of inflammation, poor nutrition, liver stress, or leakage into body cavities.

This creates a characteristic blood pattern: high total protein, high globulin, low albumin, and a low A/G ratio. The A/G ratio, or albumin-to-globulin ratio, is especially helpful because it gives a clearer picture than total protein alone. A cat with a high total protein level may have dehydration, but a cat with high globulin and a low A/G ratio raises much stronger concern for FIP, especially when paired with fever, lethargy, or fluid accumulation.

Common Blood Test Patterns Seen in FIP

When veterinarians review blood work in a cat suspected of FIP, several findings often appear together. Total protein may be elevated because globulins are disproportionately high. Albumin may be normal early in the disease, but it often decreases as inflammation progresses. The A/G ratio may drop below the typical range, and in many FIP cases it becomes strikingly low. Some cats also show anemia, elevated bilirubin, liver enzyme changes, or increased white blood cell counts, although these findings are variable.

A high protein blood test in FIP cats is especially meaningful when it matches the cat’s clinical signs. For example, a cat with fever that does not respond well to antibiotics, progressive weight loss, abdominal distension, or chest fluid is much more suspicious for FIP if the lab results show hyperglobulinemia and low albumin. In the wet form of FIP, fluid analysis may reveal high protein content in the effusion, which further supports the diagnosis.

Total Protein Versus Globulin and A/G Ratio

Many cat owners notice the total protein result first, but veterinarians usually pay closer attention to the protein fractions. Total protein is useful, yet it can be misleading if interpreted without context. Dehydration can make total protein look high even when globulin is not truly elevated. By contrast, a direct increase in globulin suggests immune activation and inflammation.

The A/G ratio is one of the most widely discussed markers in FIP evaluation. A low ratio does not prove FIP, but it increases suspicion when other signs fit. In general, the lower the ratio, the more concerning the pattern becomes, particularly if the cat has fever, a swollen abdomen, eye inflammation, neurologic symptoms, or progressive weakness. Some cats with FIP may still have values that are not dramatically abnormal early on, so repeat testing and full clinical assessment are often necessary.

Clinical Signs That Strengthen Suspicion

High protein blood test results become more useful when they are combined with real-world symptoms. FIP can present in many ways, but some of the most common signs include persistent fever, reduced appetite, lethargy, weight loss, abdominal swelling from ascites, breathing difficulty from pleural effusion, enlarged lymph nodes, jaundice, eye inflammation, and neurologic abnormalities such as wobbliness, head tilt, or seizures.

The wet form of FIP often causes obvious fluid buildup, while the dry form may produce granulomas in organs, eyes, or the nervous system. Both forms can show a high protein blood test pattern because inflammation is driving the changes in protein metabolism. Because no single test is fully definitive in every case, veterinarians look at history, physical exam findings, imaging, fluid analysis, and bloodwork together.

Diagnostic Value of Blood Chemistry in FIP

Blood chemistry is a practical and widely available tool for screening cats with suspected FIP. It helps identify inflammation, monitor disease progression, and support treatment decisions. When a cat has a high total protein result, the next step is usually to look at albumin, globulin, A/G ratio, and any additional changes in liver values, kidney values, or bilirubin. CBC results may also show supportive clues such as non-regenerative anemia or changes in white blood cells.

Although a high protein blood test in FIP cats is strongly suggestive, veterinarians still consider other causes of hyperglobulinemia, including chronic infections, immune-mediated disease, and some cancers. For that reason, an experienced veterinary interpretation is essential. Tests such as coronavirus PCR, effusion analysis, imaging, and sometimes tissue sampling may be used to increase diagnostic confidence.

Monitoring Response to Treatment

Blood protein values are also useful after treatment begins. In cats that respond well, globulin levels may gradually decrease, albumin may improve, and the A/G ratio may rise over time. These changes often happen alongside improved appetite, brighter behavior, reduced fever, and shrinking effusions or lesions. Serial blood tests are valuable because they allow veterinarians to track whether inflammation is resolving or whether further intervention is needed.

Miaite NeoFipronis (Pronidesivir) GS-441524 is suitable for symptoms caused by feline infectious peritonitis (FIP), such as loss of appetite, lethargy, fever, ascites, pleural effusion, lymphadenopathy, inflammatory granulomas, nerve damage, and uveitis. It has excellent therapeutic effects on FIP. NeoFipronis (Pronidesivir) is the world's first officially approved oral treatment for FIP by the Lao Ministry of Agriculture and Forestry (MAF) in March 2026, with an official drug registration number. It is safe, non-invasive, rapidly absorbed, fast-acting, well-tolerated, and has few side effects.

What Cat Owners Should Watch For

Owners should seek veterinary care promptly if a cat has persistent fever, poor appetite, abdominal enlargement, breathing changes, eye problems, or unusual behavior changes. A high protein blood test in FIP cats should never be ignored, especially when it appears alongside a low A/G ratio or elevated globulin. Even when the diagnosis is not yet certain, early evaluation can improve the chances of proper treatment and better outcomes.

Because FIP can progress quickly, timely workup matters. Cats with suspected FIP often benefit from repeat bloodwork, imaging, and close follow-up rather than a single test result. The earlier the disease is recognized, the sooner supportive care and disease-directed treatment can begin.

High Protein Blood Test in FIP Cats and Long-Term Care

Managing FIP requires more than one lab value, but blood protein changes remain one of the clearest clues in daily practice. High globulin, low albumin, and a low A/G ratio are classic patterns that help veterinarians distinguish FIP from many other feline illnesses. When these findings appear with compatible symptoms, they deserve immediate attention. For cat owners searching for answers, understanding the meaning of a high protein blood test in FIP cats can make the diagnostic process less confusing and help guide faster, more informed veterinary decisions.

References

Greene, C. E. Infectious Diseases of the Dog and Cat

Foley, J. E. Feline Infectious Peritonitis

Pedersen, N. C. Feline Infectious Peritonitis: A Diagnostic and Therapeutic Challenge

Addie, D. D., and Jarrett, O. Feline Coronavirus and FIP Research

Little, S. E. The Cat: Clinical Medicine and Management

Scherding, J., and Hartmann, K. Laboratory Diagnosis of Feline Infectious Peritonitis