Low Albumin in Cats: Causes, Symptoms & Treatment
Last reviewed: April 2026
Normal albumin in cats: 2.3–3.9 g/dL
Albumin keeps fluid inside blood vessels. When it drops below 2.0 g/dL, fluid can leak into the belly or chest. The cause matters as much as the number — and in cats, the albumin:globulin ratio is a critical clue.
If your cat's bloodwork shows low albumin, or your vet has mentioned hypoalbuminemia, this guide explains what it means, why it happens, and what the treatment path looks like — including the cat-specific patterns that distinguish IBD and FIP from other causes.
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Analyze My Cat's BloodworkWhat Does Albumin Do?
Albumin is the most abundant protein in blood, produced exclusively by the liver. Its primary job is maintaining oncotic pressure — the force that keeps fluid inside blood vessels rather than leaking into surrounding tissues and body cavities.
- • Holds fluid in blood vessels — when albumin drops, fluid escapes into the abdomen (ascites) or chest (pleural effusion)
- • Transports substances — carries calcium, hormones, medications, and fatty acids through the bloodstream
- • Affects calcium readings — most calcium in blood is albumin-bound, so low albumin falsely lowers total calcium; always check ionized calcium separately
- • Acts as a nutritional reserve — reflects overall protein status and nutritional adequacy
Because albumin is made in the liver and circulates in blood, it can fall from three directions: not enough being made (liver failure), too much being lost through the gut (intestinal protein loss), or too much being lost through the kidneys (kidney protein loss). In cats, there's a fourth important pattern: inflammatory protein consumption in conditions like FIP.
Albumin Severity Chart
| Albumin (g/dL) | Severity | Expected Symptoms | Typical Action |
|---|---|---|---|
| 2.3–3.9 | Normal | None | Routine monitoring |
| 2.0–2.2 | Mildly Low | Usually none visible | Check globulin, urine protein, liver values |
| 1.5–1.9 | Moderately Low | Mild fluid buildup, weight loss, lethargy | Treat cause; diuretics may help |
| Below 1.5 | Severely Low | Ascites, pleural effusion, breathing difficulty | Urgent care; plasma transfusion, fluid drainage |
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Analyze My Cat's ResultsThe Main Causes in Cats
Low albumin results from not making enough (liver failure), losing too much through the gut (intestinal protein loss), losing too much through the kidneys, or consuming it rapidly in severe inflammatory disease. The cause shapes treatment completely.
The most common cause of significantly low albumin in cats. Damaged intestinal walls leak protein — primarily albumin and globulin — into the gut lumen, where it's lost in stool. Inflammatory bowel disease (IBD) and small cell GI lymphoma are the leading drivers, and distinguishing them requires intestinal biopsy.
FIP causes low albumin through a different mechanism than intestinal loss. The coronavirus-driven inflammation consumes albumin and simultaneously drives the liver to massively overproduce globulins (acute phase proteins). The result is a pattern you won't see with PLE or liver failure: low albumin with high globulin.
The liver makes all albumin. Severe liver disease — particularly hepatic lipidosis (fatty liver) and cholangiohepatitis — can reduce albumin production. Note that albumin only drops significantly in late-stage liver disease; mildly elevated liver enzymes with normal albumin do not mean the liver can't keep up.
Cats with CKD can develop mildly low albumin through two mechanisms: reduced appetite and protein intake, and in some cases protein loss through damaged glomeruli (PLN). True PLN — where the kidney filter leaks significant albumin — is less common in cats than in dogs but does occur, particularly in Abyssinians with renal amyloidosis.
The Albumin:Globulin Ratio — A Critical Cat-Specific Clue
In cats, checking globulin alongside albumin adds crucial diagnostic information. The albumin:globulin (A:G) ratio is calculated as albumin ÷ globulin, and the pattern tells a story:
| Pattern | Albumin | Globulin | Points toward |
|---|---|---|---|
| Pan-hypoproteinemia | Low | Low | Intestinal protein loss (IBD, GI lymphoma, PLE) |
| Inverted A:G (<0.4) | Low | High | FIP (especially with effusion) |
| Selective hypoalbuminemia | Low | Normal or high | Kidney protein loss (PLN) or liver disease |
| Mild drop, all low | Mildly low | Mildly low | Poor nutrition, chronic illness, CKD |
Low albumin + low globulin
Pan-hypoproteinemia — protein leaking through the gut (IBD, GI lymphoma)
Low albumin + HIGH globulin (A:G below 0.4)
Strongly suspicious for FIP, especially in a cat with effusion
Low albumin + normal globulin
Kidney protein loss (PLN) or liver disease — check urine and liver enzymes
Why globulin matters in cats specifically
In dogs, the A:G ratio is useful but less definitive. In cats, a low albumin with high globulin and any effusion (fluid) is so characteristic of FIP that it changes the entire workup. An A:G ratio below 0.4 in a cat with ascites or pleural effusion warrants FIP testing before anything else — even before endoscopy for PLE.
Symptoms of Low Albumin in Cats
What owners notice depends on how low albumin drops and where fluid accumulates:
- • Swollen or distended abdomen — fluid accumulation (ascites); may feel fluid-filled when touched
- • Rapid or labored breathing — fluid in the chest (pleural effusion) is common in FIP and severe hypoalbuminemia
- • Progressive weight loss — even when the cat is still eating
- • Chronic vomiting or diarrhea — prominent when IBD or GI lymphoma is the cause
- • Poor appetite or anorexia — especially in liver disease and advanced cases
- • Lethargy and weakness
- • Coat changes — dull, unkempt coat from poor protein status
Note: Mildly low albumin (2.0–2.2 g/dL) often produces no visible symptoms. Many cats are diagnosed on routine bloodwork before obvious signs appear.
How to Tell the Causes Apart
Your vet will use a combination of tests to narrow down the cause:
Check globulin and calculate A:G ratio — the first and most important step. High globulin with low albumin = FIP until proven otherwise.
Urinalysis with UPC ratio — a high urine protein:creatinine ratio confirms kidney protein loss. Normal UPC rules out PLN.
Liver enzyme panel — elevated ALT, ALP, and bilirubin point toward liver disease. Low BUN in the context of low albumin is a strong liver failure clue.
Abdominal ultrasound — assesses intestinal wall thickness, liver and kidneys, lymph nodes, and confirms fluid presence. Analyzes effusion character if present.
FIP testing — if A:G ratio is low, fluid analysis (Rivalta test, PCR on fluid), FCoV antibody titers, and AGID testing help confirm FIP.
Cobalamin (B12) level — low B12 is common with small intestinal disease and affects response to treatment. Supplement if deficient.
Endoscopy with intestinal biopsy — the definitive way to distinguish IBD from small cell GI lymphoma when intestinal protein loss is suspected.
Treatment
Treatment is entirely cause-specific. There is no single approach to low albumin in cats — the right treatment depends on the diagnosis:
- For IBD-related protein loss:
- • Prednisolone (not prednisone — cats convert prednisone poorly) as the primary immunosuppressant
- • Chlorambucil added for cats who don't respond adequately to prednisolone alone, or to reduce steroid dose
- • Hydrolyzed or novel protein diet to reduce antigenic stimulation
- • B12 injections if cobalamin is deficient
- For GI lymphoma:
- • Small cell lymphoma: chlorambucil + prednisolone — responds well, median survival often 2+ years
- • Large cell lymphoma: more aggressive chemotherapy protocols (CHOP); more guarded prognosis
- For FIP:
- • GS-441524 antiviral — highly effective; most cats go into full remission with a 12-week course
- • Supportive care: drain effusions for comfort, nutritional support, B vitamins
- For hepatic lipidosis:
- • Feeding tube (esophagostomy or nasogastric) to deliver adequate calories — the liver recovers when it gets nutrition
- • Treat the underlying cause of anorexia that triggered the lipidosis
- • Liver support: SAMe, vitamin E
- For CKD / PLN:
- • Kidney-supportive diet (phosphorus restriction, moderate high-quality protein)
- • ACE inhibitors (benazepril) to reduce protein loss through damaged glomeruli
- • Subcutaneous fluids if CKD is moderate to severe
- Supportive care for severe hypoalbuminemia (any cause):
- • Plasma transfusion to temporarily raise albumin in critical cases
- • Thoracocentesis or abdominocentesis to drain effusions causing breathing difficulty
- • Diuretics (furosemide, spironolactone) to manage ongoing fluid buildup
Prednisolone, not prednisone
This matters for cats specifically. Cats have limited ability to convert prednisone to its active form, prednisolone. When treating IBD or immune-mediated conditions in cats, prednisolone is the correct choice. If your cat has been prescribed prednisone, ask your vet to confirm — many hospitals use them interchangeably by name but mean prednisolone for cats.
Prognosis
Outcomes have improved significantly across most causes. The prognosis depends more on the underlying diagnosis than on the albumin number alone:
- IBD-related PLE: Often manageable long-term with prednisolone and diet. Many cats achieve remission and require only maintenance doses.
- Small cell GI lymphoma: Responds well to chlorambucil + prednisolone. Median survival is often 2+ years with good quality of life.
- FIP: With GS-441524 antiviral treatment, the majority of cats achieve sustained remission. This disease is no longer the near-certain death sentence it once was.
- Hepatic lipidosis: Highly reversible if caught early and nutritional support is started aggressively. Survival rates above 80% with proper treatment.
- CKD-related: Depends on CKD stage and whether PLN is contributing. Many cats with CKD live well for years with appropriate management.
- Large cell GI lymphoma or end-stage liver failure: More guarded prognosis; focus shifts to quality of life.
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- ✓ Albumin and globulin — and whether the A:G ratio is inverted
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Frequently Asked Questions
What is a normal albumin level in cats?
Normal albumin in cats is 2.3–3.9 g/dL, though this varies slightly by lab. Levels below 2.0 g/dL are significant. Below 1.5 g/dL typically causes visible symptoms like fluid accumulation in the abdomen or chest.
What causes low albumin in cats?
The main causes are: IBD or GI lymphoma (protein leaking through the gut), FIP (inflammatory consumption + high globulin production), liver disease (reduced albumin production), and chronic kidney disease or PLN (protein lost in urine). Each has a distinct bloodwork pattern that helps distinguish them.
Can FIP cause low albumin in cats?
Yes. FIP causes low albumin with high globulin — an inverted A:G ratio below 0.4. This is the opposite of intestinal protein loss, which drops both albumin and globulin together. In a cat with fluid and a low A:G ratio, FIP testing should happen before anything else.
Why does my cat have a swollen belly?
When albumin drops too low, it can no longer hold fluid inside blood vessels. Fluid leaks into the abdomen (ascites), causing belly swelling. In cats this can come from IBD-related protein loss, FIP (where the fluid is thick and yellow), or severe liver disease. An ultrasound and fluid analysis help determine which.
Is low albumin in cats treatable?
Yes — and the prognosis is better than it used to be for most causes. IBD responds to prednisolone and diet. Small cell GI lymphoma often gives cats 2+ years with chemotherapy. FIP is now effectively treated with GS-441524 antivirals. Hepatic lipidosis is highly reversible with nutritional support.
Why should my cat get prednisolone instead of prednisone?
Cats have limited capacity to convert prednisone to its active form, prednisolone. When treating IBD or immune-mediated conditions in cats, prednisolone is more reliable. Many vets use both names interchangeably — confirm with your vet that your cat is receiving prednisolone.
What is the albumin:globulin ratio and why does it matter?
The A:G ratio is albumin divided by globulin. A ratio below 0.4 in a cat with fluid is highly suspicious for FIP — the virus drives globulin sky-high while albumin drops. Intestinal protein loss drops both, so the ratio stays more normal. It's one of the cheapest and fastest clues available from routine bloodwork.
What breeds of cats are prone to low albumin?
Siamese and Abyssinian cats have higher rates of IBD and GI lymphoma. Abyssinians are also predisposed to renal amyloidosis, a form of kidney protein loss. However, low albumin is much more about age and underlying disease than breed — any cat can develop hypoalbuminemia.