Alanine aminotransferase (ALT)
Chemistry ·Also called: ALT, SGPT, GPT, alanine transaminase, liver enzyme
What it is
ALT sits in the cytoplasm of liver cells. Nothing releases it while the cell is intact, so any meaningful amount in the bloodstream means liver cells have been injured or have died. It is sometimes still printed under its old name, SGPT.
Why your vet measures it
A raised ALT tells you liver cells are being damaged; it does not tell you how well the liver is working. A pet can have a high ALT and perfectly good liver function, or a failing liver with a near-normal ALT if there are few cells left to leak. Function is judged from albumin, bilirubin, glucose and bile acids instead.
What a high result can mean
- Inflammation or infection of the liver, including chronic hepatitis
- Toxins and drugs — paracetamol, xylitol, certain plants, some long-term medications
- Reduced blood or oxygen supply to the liver, as in heart failure or after an anaesthetic crisis
- Liver tumours, or cancer that has spread to the liver
- Pancreatitis or gut disease irritating the neighbouring liver tissue
- In cats, hepatic lipidosis after a period of not eating
What a low result can mean
- Not clinically significant — a low ALT is not a recognised problem
Dogs and cats differ
ALT clears from a cat's bloodstream faster than a dog's, so a feline value that is only mildly raised can still represent meaningful liver injury. In dogs, steroids and phenobarbital can lift ALT without the liver being diseased, which is why medication history matters before anyone reaches for an ultrasound.
Questions worth asking your vet
- How high is this compared with the top of the range — twice, or twenty times?
- Do the liver function markers (albumin, bilirubin, bile acids) look normal?
- Could any medication or supplement my pet is on explain this?
- Should we recheck in a few weeks before investigating further?
Related terms
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