FrançaisWhat ALT measures on your dog’s blood work
In dogs, ALT is mainly located in the fluid inside liver cells. It is called a “leakage” enzyme: it reaches the bloodstream when liver cells are damaged or when their membranes let more of it through [1].
That makes ALT a sensitive signal of liver cell injury, but not a specific one. The same increase can follow very different causes, from a medicine to inflammation of the liver, and some advanced liver conditions can even show a normal ALT when few active cells remain injured [1].
Reports may label it ALT, ALAT, GPT or SGPT. The result is given in U/L, or in µkat/L in some European laboratories. French reports use ALAT: see our French article on PAL and ALAT in dogs.
How to read the ALT line on the report
Every result line contains the same five elements. Read them together before looking at the flag.
- Abbreviation ALT, ALAT and GPT are the same test.
- Result The enzyme activity measured in this sample, at this moment.
- Unit U/L here. Check the unit before comparing with an older report from another laboratory.
- Laboratory interval The interval of healthy adult dogs for this laboratory and analyser. For comparison, the Merck Veterinary Manual lists 10–109 U/L [8]. Always use the one on your report.
- Flag H means above the interval. It describes a position, not a cause or a severity.
To describe the size of an increase, divide the result by the upper limit: here 186 ÷ 125 ≈ 1.5 times. As a guideline used in veterinary clinical pathology, an increase of 2 to 3 times the upper limit is mild, 4 to 5 times moderate and more than 10 times marked, although clinicians use slightly different cut-offs [1].
Why the size and the trend matter more than one value
The highest ALT values are usually seen with sudden injury or inflammation of the liver [1]. A mild increase is common and may have causes outside the liver, so a single result rarely settles the question.
In a study of dogs with liver lesions confirmed by biopsy, an ALT above twice the upper limit detected 40 to 65% of liver conditions. ALT, ALP or both were increased in up to 90% of cases [3]. In other words, a normal ALT does not rule everything out, and a high ALT does not name the condition.
The trend often tells more. The ACVIM consensus on chronic hepatitis in dogs describes a persistent, unexplained increase in ALT as one of the earliest laboratory signs of that condition [2]. That is why a vet may plan a repeat test after a few weeks rather than act on one number.
| Multiple of the upper limit | Usual description [1] | What it can lead to |
|---|---|---|
| Below 2× | Slight | Often a repeat test, especially if the dog is well and on medication. |
| 2 to 3× | Mild | Review of medicines and history, repeat test, other liver values. |
| 4 to 5× | Moderate | Further tests, often including imaging. |
| More than 10× | Marked | Prompt investigation, especially if the dog is unwell. |
Why ALT can be high in a dog
ALT increases fall into a few families. Your vet uses the history, the examination and other tests to tell them apart.
- Medicines. Anticonvulsants such as phenobarbital are a classic example [7]. In published series, increases in ALT occurred in about 6% of dogs given low-dose rifampicin [5] and in fewer than 10% of dogs on long-term zonisamide [6].
- Inflammation or injury of the liver. Including infections, toxins and chronic hepatitis [1, 2].
- Problems that start elsewhere. Reduced bile flow, hormonal disorders and diseases of other abdominal organs can affect liver cells secondarily [1].
- Trauma and severe muscle injury. A blow or a major muscle condition can raise ALT; muscle damage also raises other enzymes such as CK and AST [1].
What can affect an ALT result
- Age: puppies tend to have lower ALT than adult dogs, so age-appropriate interpretation matters [4].
- Red cells broken during sampling (haemolysis) have little effect on ALT in dogs, unlike in cats [1].
- Recent medicines, supplements and possible access to toxins, such as household products, plants or someone else’s medication.
- Different laboratories or analysers between two tests: compare trends on the same method when possible.
The values often read with ALT
Comparing how much each liver value has risen helps your vet suggest which process came first: liver cell injury or reduced bile flow [1].
When ALT stays high, see liver disease in dogs.
En français : aLAT élevée chez le chien.
Questions to ask your veterinarian
- How many times above the upper limit is my dog’s ALT, and is it higher or lower than last time?
- Could any of my dog’s medicines or supplements be involved?
- What do the ALP, bilirubin and albumin results add to the picture?
- When should we repeat the test, and what result would change the plan?
- Would imaging or a liver function test such as bile acids help, and why?
Get your dog’s whole report explained, value by value.
ALT is one line among many. AI DiagAnimals reads the full report with its own intervals and units, links the related values and prepares the questions for your vet. The service opens soon: leave your email to be told first.
Frequently asked questions
When should I worry about ALT in dogs?
Contact your vet promptly if the dog is unwell, whatever the number. In a dog that seems well, the size of the increase and its trend guide the next step: a slight increase is often rechecked, a marked one investigated quickly [1, 2].
What is an alarming ALT level in a dog?
There is no single threshold. Pathologists describe more than 10 times the upper limit as a marked increase [1], but a moderate increase that persists can also matter, and a severe liver condition can sometimes have a normal ALT [1].
Can a dog’s liver recover after a high ALT?
The liver has a strong capacity to regenerate, and ALT often returns to the interval once a temporary cause, such as a medicine, has been addressed. How far it recovers depends on the cause, which is what your vet investigates.
What is the life expectancy of a dog with high liver enzymes?
An enzyme value alone does not predict life expectancy. Many dogs with a mild increase live normally. The outlook depends on the cause, the dog’s condition and the response to the plan your vet proposes.
How do I lower my dog’s ALT?
Treatment targets the cause, not the number. Do not start a supplement or change the diet without your vet’s advice, especially if your dog takes other medicines.
Sources
- eClinPath, Cornell University College of Veterinary Medicine. Alanine aminotransferase (ALT). eclinpath.com/chemistry/liver/liver-injury/alanine-aminotransferase
- Webster CRL et al. ACVIM consensus statement on the diagnosis and treatment of chronic hepatitis in dogs. J Vet Intern Med. 2019;33(3):1173-1200. doi.org/10.1111/jvim.15467
- Assawarachan SN et al. A descriptive study of the histopathologic and biochemical liver test abnormalities in dogs with liver disease in Thailand. Can J Vet Res. 2020;84(3):217-224. pubmed.ncbi.nlm.nih.gov/32801457
- Montoya Navarrete AL et al. Effect of age, sex, and body size on the blood biochemistry and physiological constants of dogs from 4 wk to > 52 wk of age. BMC Vet Res. 2021;17:265. doi.org/10.1186/s12917-021-02976-w
- Harbour L et al. Rifampicin treatment of canine multidrug-resistant meticillin-resistant staphylococcal pyoderma: a retrospective study of 51 cases. Vet Dermatol. 2022;33(5):384-391. doi.org/10.1111/vde.13105
- Smith TK et al. Incidence of hepatopathies in dogs administered zonisamide orally. J Vet Intern Med. 2022;36(2):576-579. doi.org/10.1111/jvim.16398
- eClinPath, Cornell University College of Veterinary Medicine. Alkaline phosphatase (ALP). eclinpath.com/chemistry/liver/cholestasis/alkaline-phosphatase
- 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.