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High liver enzymes in cats: reading ALT, ALP and bilirubin in your cat

Liver enzymes do not behave in cats as they do in dogs. A small rise in ALP can matter, steroids do not raise it, and an overactive thyroid can mimic liver disease. Here is how to read the liver lines on your cat’s chemistry panel.

Written by the AI DiagAnimals editorial teamReviewed by the AI DiagAnimals TeamUpdated Our editorial policy

The essentials

In cats, ALT rises when liver cells are injured, and ALP is specific to the liver and bile ducts but rises only modestly, so even a small increase deserves attention. The most dramatic ALP rises come from fatty liver (hepatic lipidosis), often without a rise in GGT. Hyperthyroidism commonly causes mild increases in ALT and ALP. Haemolysis in the sample can falsely raise ALT.

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The liver lines on a cat’s panel

LineWhat it reflects in cats
ALTInjury to liver cells. It is cleared within hours in cats (half-life 2.8–4.4 h), much faster than in dogs [1].
ALPBile flow problems. Specific to the liver in cats, but less sensitive than in dogs; its half-life is about 6 hours [2].
GGTAnother bile-duct enzyme; read with ALP to sort out the pattern [2].
BilirubinThe yellow pigment; high values cause jaundice.

How to read the ALP line

Here is an example line from a cat’s chemistry panel.

An annotated line from a lab report · Illustrative example
AbbreviationResultUnitLaboratory intervalFlag
ALP Alkaline phosphatase96U/L0–45H
  1. Abbreviation ALP, ALKP or PAL on French reports.
  2. Result 96 U/L in this illustrative line: a modest rise, but meaningful in a cat [2].
  3. Unit U/L or IU/L; some European laboratories use µkat/L (U/L × 0.0167) [2].
  4. Laboratory interval The example uses the cat interval of the Merck Veterinary Manual (ALT 25–97 U/L, ALP 0–45 U/L) [3].
  5. Flag H: above the interval. Your vet reads it with ALT, GGT, bilirubin and the thyroid value (T4) [2].

Why cats are different from dogs

  • Small ALP rises count. Cat liver cells contain little ALP and it is cleared quickly, so many vets do not ignore small increases [2].
  • No steroid effect. In dogs, corticosteroids raise ALP; this effect is not reported in cats [2].
  • ALP can be normal despite liver disease. In cats with liver disease, ALP was raised less often than ALT [2].
  • Haemolysis. Broken red cells in the sample can raise ALT in cats, with little effect in dogs [1].

Common causes of high liver enzymes in cats

  • Fatty liver (hepatic lipidosis). Often in cats that have stopped eating; it causes the most dramatic ALP rises, often without a rise in GGT [2].
  • Cholangitis and bile duct disease, including obstruction [2].
  • Pancreatitis, because cats share a common duct for bile and pancreatic juice [2].
  • Hyperthyroidism. It often causes mild increases in ALT, AST and ALP, mostly bone ALP, without a rise in GGT; ALP falls with successful treatment [1, 2].
  • Liver tumours such as lymphoma, and some drugs [1, 2].

Young growing cats can have a higher ALP from bone growth [2].

Results often read with the liver enzymes

T4 (thyroid)

Measured in older cats to rule out hyperthyroidism as the cause.

Lipase (fPL)

Checks for pancreatitis, which often accompanies liver and gut disease in cats.

Read the article

Cat blood work overview

All the lines of a cat’s panel and the cat-specific pitfalls.

Read the article

For dogs, see high liver enzymes in dogs.

A high ALP with a normal GGT in a cat that stopped eating: hepatic lipidosis.

En français : aLAT et PAL élevées chez le chat.

Questions to ask your veterinarian

  1. Which enzymes are high, and by how much compared with the upper limit?
  2. Is GGT raised as well, or only ALP?
  3. Could hyperthyroidism explain the result? Has T4 been measured?
  4. Could the sample have been haemolysed?
  5. Is an ultrasound or a repeat test needed, and when?
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Frequently asked questions

What does it mean if my cat has elevated ALT?

ALT leaks from injured liver cells. In cats it is cleared within hours, so a high value reflects recent or ongoing injury. Haemolysis in the sample can also raise it [1].

When should I worry about high liver enzymes in my cat?

Any ALP rise deserves attention in a cat, as do marked ALT rises, jaundice, a cat that stops eating or weight loss. Your vet will decide which tests come next [1, 2].

Can hyperthyroidism raise liver enzymes in cats?

Yes. Hyperthyroid cats often have mild increases in ALT and ALP, which improve when the thyroid is treated [1, 2].

How long can a cat live with liver disease?

It depends on the cause. Many causes, such as fatty liver treated early or cholangitis, can be managed or resolved.

Why is ALP more important in cats than in dogs?

Cat liver cells contain little ALP and it is cleared within about 6 hours, so even a small increase can point to liver or bile duct disease [2].

Sources

  1. eClinPath, Cornell University College of Veterinary Medicine. Alanine aminotransferase. eclinpath.com/chemistry/liver/liver-injury/alanine-aminotransferase
  2. eClinPath, Cornell University College of Veterinary Medicine. Alkaline phosphatase. eclinpath.com/chemistry/liver/cholestasis/alkaline-phosphatase
  3. Merck Veterinary Manual. Serum biochemical analysis reference ranges. merckvetmanual.com/reference-values-and-conversion-tables/reference-guides/serum-biochemical-analysis-reference-ranges

Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.

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