What Does ALT Mean in Dogs and Cats?
Quick answer
ALT is an enzyme found mainly inside liver cells. When those cells are irritated or damaged, ALT leaks into the blood and the value rises. A high ALT signals liver stress, not a specific disease, so vets look at how high it is, the trend over time, and related markers.
What is ALT?
Alanine aminotransferase is an enzyme concentrated in liver cells in both dogs and cats, making it one of the most liver-specific enzymes on a routine panel.
Reference range
[Range pending sourced table] Reference ranges vary by lab and species. Use the range printed on your pet's report.
What can raise ALT
- Liver inflammation or infection
- Some medications
- Toxins
- Hormone conditions such as Cushing's disease or hyperthyroidism
- Reduced blood flow to the liver
- Muscle injury (mild effect)
What can lower ALT
- Low values are rarely significant
- Advanced liver scarring with few remaining cells
Dogs vs cats
In dogs
Mild ALT rises are common in dogs on certain medications or with hormone conditions.
In cats
Cats have less ALT than dogs, so even moderate increases can matter more and deserve follow-up.
Why one value rarely tells the whole story
ALT shows that liver cells are stressed but not how well the liver works or why. Hydration, recent meals, stress during the visit, medications, and how the sample was handled can all shift a result. Vets look at the whole panel, your pet's symptoms, and the trend across tests over time.
Conventional interpretation
Vets weigh how far above range ALT is, whether it is rising, and companion markers such as ALP, GGT, bilirubin, and albumin. Persistent increases often prompt function testing or imaging.
Whole-pet context
Consider recent medications, diet changes, chew toys or plants that could expose your pet to toxins, and energy and appetite at home.
Supportive options are not a cure. Check with your veterinarian before adding any supplement.
Questions to ask your vet
- Should we recheck ALT, and when?
- Could any medication or supplement explain this?
- Do we need bile acids or an ultrasound?
- How does this compare with my pet's previous results?
Frequently asked questions
Does high ALT mean liver failure?
- No. It means liver cells are stressed. Liver function is assessed with other tests such as bile acids, albumin, and bilirubin.
Can ALT come back down?
- Often, yes, once the cause is found and managed. Rechecks show whether it is improving.
What is a normal ALT range?
- Reference ranges vary by laboratory, analyzer, and species. Use the range printed on your pet's report and ask your vet how your pet's result compares.
Should ALT be rechecked?
- Your veterinarian decides based on how far from range the value is, your pet's symptoms, and other results. Trends over time are often more useful than one result.
Related lab values
Related guides
Educational support only. Not a diagnosis or substitute for veterinary care.
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