Hyperlipidaemia — the presence of abnormally elevated lipids (fats) in the blood — is less commonly discussed in feline medicine than in dogs or humans, but it is a clinically important condition that warrants recognition, investigation, and appropriate management. In cats, hyperlipidaemia may present as an incidental finding on routine blood panels or as the underlying cause of specific, sometimes puzzling clinical signs including peripheral neuropathy, skin xanthomas, and Horner syndrome.

Unlike in humans, where primary hypercholesterolaemia driven by dietary fat intake and genetics is the most common scenario, feline hyperlipidaemia is most frequently secondary to another underlying disease. Identifying and treating the primary cause is therefore the first and most important step in management.

Lipid Metabolism in Cats

Cats are obligate carnivores with a metabolism adapted for high fat and protein intake and relatively minimal carbohydrate metabolism. Dietary lipids are absorbed from the intestine and transported in the circulation as lipoproteins — protein-lipid complexes that enable fat to circulate in the aqueous blood environment. The major lipoproteins in cats include chylomicrons (transporting dietary triglycerides from the gut), very low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL).

Normal fasting blood lipid levels in cats are: total cholesterol 2.0 to 3.6 mmol/L (77–140 mg/dL) and triglycerides below 1.1 mmol/L (below 100 mg/dL). Post-prandial (non-fasting) lipid levels are transiently elevated; blood samples for lipid assessment should always be taken after a minimum 12-hour fast to avoid misclassification of physiological post-prandial lipaemia as pathological hyperlipidaemia.

Important: Always Fast Before Lipid TestingBlood for cholesterol and triglyceride measurement must be collected after a minimum 12-hour fast. Post-prandial lipaemia can transiently raise triglycerides to 5–10 times fasting levels and may appear as grossly lipaemic (milky white) serum, causing confusion with true pathological hyperlipidaemia.

Primary vs. Secondary Hyperlipidaemia

Primary (Idiopathic) Hyperlipidaemia

Primary idiopathic hyperlipidaemia is recognised in cats but is considerably less common than secondary forms. It is characterised by elevated blood lipids in the absence of any identifiable underlying disease. A hereditary basis has been proposed and is well established in certain strains of cats, where a lipoprotein lipase (LPL) deficiency leads to failure to clear chylomicrons and triglyceride-rich lipoproteins from the blood after a meal. Affected cats may have markedly elevated triglycerides (often above 10 to 20 mmol/L) and grossly lipaemic serum at rest.

Secondary Hyperlipidaemia

Secondary hyperlipidaemia — elevation of blood lipids as a consequence of another underlying condition — is the more common presentation in feline clinical practice. The most important secondary causes include:

• Diabetes mellitus: Insulin deficiency or resistance impairs the activity of lipoprotein lipase (the enzyme that clears triglycerides from the blood) and promotes mobilisation of free fatty acids from adipose tissue. Hypertriglyceridaemia and hypercholesterolaemia are both common in uncontrolled diabetic cats.
• Hypothyroidism: Rare in cats (unlike in dogs), but reduced thyroid hormone levels decrease LDL receptor expression, impairing cholesterol clearance and causing hypercholesterolaemia.
• Cholestatic liver disease: Bile duct obstruction impairs bile acid excretion, causing cholesterol accumulation. Elevated total cholesterol is common in cats with biliary tract disease.
• Pancreatitis: Hypertriglyceridaemia can both cause and result from pancreatitis, creating a bidirectional relationship. Severely elevated triglycerides are directly toxic to pancreatic acinar cells.
• Nephrotic syndrome: Protein loss through damaged glomeruli stimulates hepatic lipoprotein synthesis, causing both hypercholesterolaemia and hypertriglyceridaemia.
• High-fat dietary intake: Though cats tolerate dietary fat well compared to dogs, consistently very high-fat diets — particularly in cats with concurrent metabolic disease — can contribute to hyperlipidaemia.

Clinical Signs

Many cats with hyperlipidaemia are completely asymptomatic, with the abnormality detected incidentally on routine blood panels. However, significant or prolonged hyperlipidaemia can produce several distinctive and sometimes severe clinical signs:

Xanthomas

Xanthomas are lipid-laden macrophage (foam cell) deposits that form in skin and soft tissues when circulating lipid levels are grossly elevated. In cats, they most commonly appear as firm, non-painful, yellowish to white nodules or plaques — most frequently over pressure points (elbows, stifles, paws, pinnae) and sometimes at previous injection or trauma sites. They may ulcerate. Xanthomas are pathognomonic of severe hyperlipidaemia and their presence should prompt urgent investigation of the underlying cause.

Peripheral Neuropathy

Lipid infiltration of peripheral nerves — specifically the myelin sheath — can cause neuropathy in cats with severe hyperlipidaemia. Clinical signs include hindlimb weakness, abnormal gait, and sensory deficits. Horner syndrome (miosis, ptosis, enophthalmos, and protrusion of the third eyelid) can result from lipid infiltration affecting the sympathetic nerve supply to the eye. The neuropathy is generally reversible with effective lipid-lowering treatment.

Gastrointestinal Signs

Abdominal pain, vomiting, and diarrhoea can occur, particularly in association with hyperlipidaemia-associated pancreatitis. Hepatic lipidosis — a potentially fatal accumulation of fat within liver cells — can develop in cats with prolonged severe hypertriglyceridaemia and concurrent anorexia.

Lipaemic Serum

Grossly lipaemic serum — appearing milky white or turbid rather than the normal pale yellow colour — reflects very high circulating triglyceride and chylomicron levels. Lipaemia interferes with many routine blood tests, causing spurious results in haematology, biochemistry, and urinalysis panels. A lipaemic serum sample should always prompt investigation rather than simply being noted as a technical finding.

Diagnosis

The diagnostic approach to suspected hyperlipidaemia follows a logical sequence:

Step 1: Confirm True Hyperlipidaemia

Ensure a fasting blood sample (minimum 12 hours) has been taken. Measure fasting cholesterol and triglycerides. Reference ranges: total cholesterol 2.0 to 3.6 mmol/L; triglycerides below 1.1 mmol/L. Values consistently above these ranges on two or more separate fasting samples confirm true hyperlipidaemia.

Step 2: Identify Secondary Causes

A comprehensive investigation for secondary causes should be completed before primary hyperlipidaemia is diagnosed. This includes:

• Blood glucose (fasting) and fructosamine — diabetes mellitus
• Total T4 (thyroxine) — hypothyroidism (rare in cats; always consider in appropriate presentation)
• Full biochemistry panel including liver enzymes, bilirubin, GGT — hepatic disease
• Pancreatic lipase immunoreactivity (fPLI) — pancreatitis
• Urinalysis and urine protein:creatinine ratio — nephrotic syndrome
• Dietary history — assess fat content and feeding practices

Step 3: Lipoprotein Electrophoresis

In cats where secondary causes have been excluded, lipoprotein electrophoresis can characterise the lipid profile more precisely — identifying whether cholesterol or triglycerides predominate and which lipoprotein fractions are abnormally elevated. This helps differentiate LPL deficiency (chylomicronaemia syndrome) from other forms of primary hyperlipidaemia and can guide specific dietary and pharmacological management.

Management

Treat the Underlying Cause

In secondary hyperlipidaemia, effective management of the primary condition typically leads to normalisation or significant improvement of lipid levels. Glycaemic control in diabetic cats, treatment of hepatic or pancreatic disease, and resolution of nephrotic syndrome will usually reduce lipid levels substantially without the need for specific lipid-lowering therapy.

Dietary Management

Dietary fat restriction is the first-line intervention for both primary and persistent secondary hyperlipidaemia. A low-fat diet (fat content below 20% metabolisable energy) reduces chylomicron and VLDL production and lowers triglyceride levels. In cats with LPL deficiency, a very low-fat diet — sometimes below 10% metabolisable energy — may be required to prevent postprandial chylomicronaemia.

Omega-3 fatty acid supplementation (EPA and DHA from marine fish oil) has triglyceride-lowering effects through reduced hepatic VLDL synthesis and enhanced triglyceride clearance. Supplementation at 50 to 100 mg/kg/day combined EPA + DHA is commonly recommended, though owner compliance and palatability can be limiting factors.

Pharmacological Treatment

Lipid-lowering drugs are reserved for cats with persistent, clinically significant hyperlipidaemia despite dietary management and treatment of any underlying cause. The evidence base in cats is more limited than in dogs or humans, and drug selection requires individual consideration:

• Fibrates (gemfibrozil, bezafibrate): Activate peroxisome proliferator-activated receptor alpha (PPAR-alpha), increasing lipoprotein lipase activity and reducing hepatic VLDL synthesis. Most effective for hypertriglyceridaemia. Gemfibrozil at 7.5 mg/kg q12h has been used in cats with some success, though hepatotoxicity monitoring is required.
• Statins (atorvastatin): Inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol synthesis. Most effective for hypercholesterolaemia. Feline-specific pharmacokinetic data are limited; use with caution and regular liver enzyme monitoring.
• Niacin (nicotinic acid): Reduces hepatic VLDL synthesis and free fatty acid mobilisation. Used at low doses in cats; flushing reactions seen in humans are less common in cats. Evidence in feline hyperlipidaemia is largely anecdotal.

Lipid Abnormality	Primary Intervention	Second-Line / Adjunct
Hypertriglyceridaemia	Low-fat diet; treat underlying cause (diabetes, pancreatitis)	Omega-3 supplementation; fibrates (gemfibrozil)
Hypercholesterolaemia	Treat underlying cause (hepatic disease, hypothyroidism)	Dietary fat restriction; statins in refractory cases
Mixed hyperlipidaemia	Dietary fat restriction; treat underlying cause	Omega-3 supplementation; fibrates or statins as appropriate
LPL deficiency (chylomicronaemia)	Very low-fat diet (< 10% ME from fat) as primary therapy	No effective pharmacotherapy; strict dietary adherence essential

Monitoring

Cats receiving treatment for hyperlipidaemia should be reassessed with fasting lipid profiles every 2 to 3 months initially, then every 6 months once stable. Cats on fibrates or statins require liver enzyme monitoring every 3 months. Clinical response — resolution of xanthomas, improvement in neurological signs, and owner-reported quality of life improvement — should be assessed at each visit alongside laboratory values.

In cats with secondary hyperlipidaemia, monitoring of the primary disease (diabetes, CKD, hepatic disease) follows the protocols appropriate to that condition.

Key Takeaways

• Feline hyperlipidaemia is most commonly secondary to diabetes, hepatic disease, pancreatitis, or nephrotic syndrome — identify and treat the primary cause first
• Always use fasting blood samples (minimum 12 hours) for accurate lipid measurement — post-prandial lipaemia causes significant transient elevation
• Xanthomas and peripheral neuropathy (including Horner syndrome) are hallmark complications of severe hyperlipidaemia
• Dietary fat restriction and omega-3 supplementation are the foundations of lipid management
• Pharmacological treatment (fibrates, statins) is reserved for persistent hyperlipidaemia after dietary management and treatment of underlying causes
• Regular monitoring of lipid levels and liver enzymes is required for cats on lipid-lowering medications

References

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2. Watson TD, Barrie J (1993). Lipoprotein metabolism and hyperlipidaemia in the dog and cat: a review. J Small Anim Pract 34(10):479–87.

3. Jones BR et al. (1986). Inherited hyperchylomicronaemia in the cat. J Small Anim Pract 27(9):521–53.

4. Vitale CL, Ihrke PJ (1994). Xanthoma formation associated with hyperlipidaemia in cats: a retrospective case series. Vet Dermatol 5(4):169–76.

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6. Sykes JE (2014). Canine and Feline Infectious Diseases. Elsevier Saunders. [Background lipid physiology reference]