ALP (alkaline phosphatase) is an enzyme found in bile ducts, bone, and other tissues. In cats, ALP is highly specific for liver and bile duct disease because cats lack the steroid-induced isoenzyme that causes benign elevations in dogs. Normal range: 14-111 U/L.

What is normal ALP range for cats?

Normal ALP range for cats is typically 14-111 U/L. The short half-life in cats (about 6 hours vs 70+ hours in dogs) means any ALP elevation reflects active, ongoing disease and should be investigated.

What causes high ALP in cats?

Common causes include hepatic lipidosis (fatty liver, 80%+ have elevated ALP), cholangiohepatitis, bile duct obstruction, hyperthyroidism, liver tumors, and pancreatitis. The pattern with GGT helps distinguish: high ALP with normal GGT suggests hepatic lipidosis; high ALP with high GGT suggests cholangitis.

What does high ALP with normal GGT mean in cats?

High ALP with normal or low GGT is considered nearly pathognomonic (highly characteristic) for hepatic lipidosis (fatty liver disease). This pattern helps distinguish hepatic lipidosis from cholangiohepatitis, where both ALP and GGT are elevated.

When should I worry about ALP in cats?

Worry when: ALP is elevated at all (unlike dogs, there are no benign causes in cats), your cat has stopped eating (hepatic lipidosis risk), your cat shows symptoms like jaundice, lethargy, or vomiting, or ALP is elevated with other liver enzymes.

What is the ALP to GGT ratio in cats?

The ALP:GGT relationship helps diagnose liver conditions. High ALP with normal/low GGT = hepatic lipidosis. High ALP with high GGT = cholangitis or bile duct obstruction. This pattern is clinically useful for narrowing the diagnosis.

ALP in Cats: Normal Range, What High Levels Mean & When to Worry

Quick Answer: Normal ALP in Cats

Normal ALP range: 14-111 U/L. Unlike dogs, any ALP elevation in cats is clinically significant. Cats lack the steroid-induced ALP isoenzyme that causes benign elevations in dogs, so high ALP always warrants investigation.

If your cat's bloodwork shows elevated ALP, this is more significant than it would be in a dog. This guide explains why ALP matters so much in cats, what causes elevations, and what steps to take next.

What is ALP in Cats?

ALP (Alkaline Phosphatase) is an enzyme found in bile ducts, bone, and intestinal tissue. In cats, the hepatic (liver) and bone isoforms are the primary sources of blood ALP.

The critical difference between cats and dogs: dogs produce a glucocorticoid-induced ALP isoenzyme that causes high ALP from steroids, stress, or Cushing's disease. Cats do NOT produce this isoenzyme. This means:

In dogs: High ALP can be benign (steroids, medications, breed variations)
In cats: High ALP almost always indicates real hepatobiliary disease

Additionally, ALP has a much shorter half-life in cats (about 6 hours) compared to dogs (70+ hours). This means any ALP elevation requires active, ongoing disease to maintain it — making even modest elevations clinically important.

ALP Severity Chart: Understanding Your Cat's Results

14-111 U/L

Normal

Meaning: Bile duct and liver function within normal range

Action: Routine monitoring as part of wellness exams

112-222 U/L

Mild

Meaning: Early liver/biliary stress — investigate cause (up to 2x normal)

Action: Check GGT, thyroid, ensure cat is eating well

223-555 U/L

Moderate

Meaning: Significant hepatobiliary disease — often hepatic lipidosis or cholangitis (2-5x normal)

Action: Ultrasound, GGT comparison, nutritional support if needed

556-1110 U/L

Severe

Meaning: Severe hepatic lipidosis, cholangitis, or bile duct obstruction (5-10x normal)

Action: Urgent intervention, often hospitalization, aggressive feeding support

>1110 U/L

Critical

Meaning: Severe hepatic lipidosis or complete bile duct obstruction (>10x normal)

Action: Emergency care, IV fluids, feeding tube likely needed

ALP Level (U/L)	Severity	What It Means	Typical Action
14-111	Normal	Bile duct and liver function within normal range	Routine monitoring as part of wellness exams
112-222	Mild	Early liver/biliary stress — investigate cause (up to 2x normal)	Check GGT, thyroid, ensure cat is eating well
223-555	Moderate	Significant hepatobiliary disease — often hepatic lipidosis or cholangitis (2-5x normal)	Ultrasound, GGT comparison, nutritional support if needed
556-1110	Severe	Severe hepatic lipidosis, cholangitis, or bile duct obstruction (5-10x normal)	Urgent intervention, often hospitalization, aggressive feeding support
>1110	Critical	Severe hepatic lipidosis or complete bile duct obstruction (>10x normal)	Emergency care, IV fluids, feeding tube likely needed

Remember: even mild ALP elevations in cats should be investigated. The short half-life (6 hours) means any elevation requires ongoing disease to maintain it.

The ALP-GGT Pattern: Diagnosing Liver Disease

One of the most useful diagnostic patterns in feline liver disease is comparing ALP with GGT levels:

High ALP + Normal/Low GGT: Strongly suggests hepatic lipidosis (fatty liver). This pattern is considered nearly pathognomonic (highly characteristic) for hepatic lipidosis in cats.
High ALP + High GGT: Suggests cholangitis/cholangiohepatitis or bile duct obstruction. The elevated GGT confirms bile duct involvement beyond hepatic lipidosis.

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Common Causes of High ALP in Cats

Hepatic Lipidosis (Fatty Liver): The most common cause. Over 80% of cats with hepatic lipidosis have elevated ALP, often 2-5x normal or higher. Pattern: high ALP, normal GGT.
Cholangitis/Cholangiohepatitis: Inflammation of bile ducts and liver. Second most common liver disease in cats. Pattern: high ALP AND high GGT.
Bile Duct Obstruction: Blockage from stones, tumors, or inflammation. Causes marked ALP and GGT elevation.
Hyperthyroidism: Very common in older cats. Causes mild ALP elevation, primarily from bone isoenzyme due to increased bone turnover.
Pancreatitis: Often occurs alongside liver/bile duct disease (triaditis) in cats.
Liver Tumors: Lymphoma is the most common liver cancer in cats.

Hepatic Lipidosis: The #1 Cause of High ALP in Cats

Hepatic lipidosis (fatty liver disease) deserves special attention because it's unique to cats and is the most common liver disease in the species.

When a cat stops eating for any reason, the body mobilizes fat stores for energy. In cats, this fat floods the liver faster than it can be processed, causing liver failure. The hallmark bloodwork finding is:

• ALP elevated 2-5x normal or higher (seen in 80%+ of cases)
• GGT normal or only slightly elevated
• ALT often elevated (but ALP typically higher than ALT)

Any cat that stops eating for more than 24-48 hours is at risk. Overweight cats are especially vulnerable. Treatment requires aggressive nutritional support, often via feeding tube.

Why Cats Are Different from Dogs

The differences in ALP between cats and dogs are clinically significant:

No steroid-induced isoenzyme: Dogs produce excess ALP when stressed or on steroids. Cats don't — so no benign elevations.
Short half-life (6 hours vs 70+ hours): ALP drops quickly in cats when disease resolves. Ongoing elevation requires ongoing damage.
Lower baseline levels: Cat hepatocytes contain less ALP than dog hepatocytes, so even small increases are significant.

Symptoms Pet Owners Might Notice

Cats with elevated ALP may show:

• Loss of appetite (critical warning sign — can trigger hepatic lipidosis)
• Lethargy or hiding
• Vomiting
• Weight loss
• Jaundice — yellow eyes, gums, or ear flaps
• Increased thirst and urination
• Abdominal discomfort

Note: Cats are masters at hiding illness. A cat may have significantly elevated ALP before showing obvious symptoms. Regular bloodwork helps catch problems early.

What Happens Next?

Your veterinarian may recommend:

• Check GGT — the ALP:GGT pattern helps diagnose hepatic lipidosis vs cholangitis
• Check ALT and AST — assess liver cell damage
• Thyroid testing (T4) — hyperthyroidism is very common in older cats
• Bilirubin — assess bile flow
• Abdominal ultrasound — visualize liver structure, check for fatty infiltration
• Ensure adequate nutrition — critical to prevent or treat hepatic lipidosis
• Consider feeding tube — if cat isn't eating, early tube feeding saves lives

Key Takeaway

ALP elevation in cats is never benign. Always investigate.

The ALP-GGT pattern is invaluable: high ALP with normal GGT suggests hepatic lipidosis (focus on nutrition), while high ALP with high GGT suggests cholangitis (likely needs anti-inflammatories or antibiotics).

Track Your Cat's ALP Levels

Upload your bloodwork to VetLens and instantly see:

✓ What your cat's specific ALP level means
✓ The ALP-GGT pattern and what it suggests
✓ Whether hepatic lipidosis risk factors are present
✓ Questions to ask your vet at the next visit

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Frequently Asked Questions

Why is high ALP more serious in cats than dogs?

Dogs can have benign ALP elevations from steroids, medications, or breed variations. Cats lack the glucocorticoid-induced ALP isoenzyme, so any elevation indicates real hepatobiliary disease.

What does high ALP with normal GGT mean?

This pattern is nearly pathognomonic for hepatic lipidosis (fatty liver disease). It helps distinguish hepatic lipidosis from cholangitis, where both ALP and GGT are elevated.

Can hyperthyroidism cause high ALP in cats?

Yes. Hyperthyroidism can cause mild ALP elevation, primarily from the bone isoenzyme due to increased bone turnover. This typically resolves with hyperthyroidism treatment.

What is a normal ALP level in cats?

Normal ALP range is typically 14-111 U/L, though this varies by laboratory and testing method.

Why does ALP have a short half-life in cats?

ALP is cleared more rapidly in cats (6-hour half-life) compared to dogs (70+ hours). This means any sustained elevation requires ongoing active disease, making even modest elevations clinically significant.

Is hepatic lipidosis treatable?

Yes, with aggressive nutritional support. Cats with hepatic lipidosis often need feeding tubes to ensure adequate caloric intake. With proper treatment started early, the prognosis is good — survival rates exceed 80% in treated cats.

What is triaditis in cats?

Triaditis is the concurrent inflammation of the liver (hepatitis), pancreas (pancreatitis), and intestine (inflammatory bowel disease). It's common in cats because these organs share bile duct anatomy. ALP is often elevated in triaditis.

Can ALP levels return to normal in cats?

Yes. Because of the short 6-hour half-life, ALP normalizes quickly once the underlying disease is addressed. Serial monitoring can track treatment response.