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If your dog's bloodwork came back with high liver enzymes, the first thing worth knowing is what that result actually is. It's a flag. Something in or around the liver has changed, and the number by itself doesn't tell me what. A lot of the dogs I see with this result turn out to be fine.
Key Takeaways
Come in today if: your dog's gums, eyes or skin look yellow, they're vomiting or off their food, their belly looks swollen, their stool is black and tarry, they seem confused or unsteady, or they've eaten xylitol, a sago palm or wild mushrooms. High enzymes in a sick dog is a different problem than high enzymes in a well one. Book online or call (519) 896-0532.
Liver enzymes are proteins the liver uses to do its work, which includes processing food, storing energy and filtering drugs and toxins out of the blood.
They're meant to stay inside the cells. When liver cells are damaged or irritated, some of that content leaks into the bloodstream and the lab picks it up. That leak is what an elevated result is actually showing you.
Four of them show up on a standard canine panel, and they don't all mean the same thing. Reading them as a single number is where most of the worry comes from.
| Enzyme | Where it comes from | What a high level usually points to |
|---|---|---|
| ALT alanine aminotransferase | Mostly liver cells | Liver cells have been damaged or irritated. The most liver-specific of the four.1 |
| AST aspartate aminotransferase | Liver cells and muscle | Usually moves with ALT. A high AST alongside a normal ALT often points at muscle rather than liver.1 |
| ALP alkaline phosphatase | Liver, bile ducts, bone, plus a steroid-driven form | Bile flow has slowed, a drug has switched on production, or a puppy's bones are growing.1 |
| GGT gamma-glutamyl transferase | Mainly the bile ducts | Bile flow is affected. Less sensitive than ALP, but when it's up it's more specific to the biliary system.1 |
The pattern tells me more than any single value does. A high ALT with a normal ALP reads completely differently from a high ALP and GGT with a normal ALT. The first points at the liver cells. The second points at bile flow.
When I see high liver enzymes I sort the possibilities into two piles. Problems in the liver, and problems somewhere else that the liver is reacting to. The second pile is bigger than most owners expect.
The liver filters blood from the whole body, so it reacts to things that have nothing to do with the liver itself. Most of these produce a harmless change called vacuolar hepatopathy. The enzymes go up and the liver carries on working normally.3
In a dog who feels well, a single high liver enzyme is not an emergency, and I wouldn't jump to a biopsy over it.
What I want to know is whether it stays up. The specialist consensus on chronic liver disease in dogs points to an unexplained ALT still elevated after 2 months as the most useful early screening finding.2 One result doesn't tell me much. Two results a couple of months apart tell me which direction this is heading, which is why I'll usually recheck before doing anything more involved.
Assuming your dog is bright, eating normally, fine on physical exam and not on a medication that explains it, this is roughly the order I work through:
Antioxidants like SAMe and bile acid medications like ursodiol often get started somewhere in here. The catch is that starting them before the recheck muddies the recheck, so I'd get the baseline first.
There are a few situations where I see a raised enzyme and don't chase it.
The most common by a distance is a dog already on a steroid or on phenobarbital. Prednisone raises ALP within 5 to 7 days of the first dose, and that's the drug doing what it does rather than a new liver problem.1 The values drift back down once the course ends.
Growing puppies are the next one. Bone is one of the places ALP comes from, and a puppy building a skeleton makes plenty of it.1 A raised ALP on its own in a bright, growing pup is usually just that. If the ALT is up as well, I'd look further.
Then there's the older dog with a mildly high ALP and nothing else going on. Benign nodules are close to universal by that age.4 If the exam is clean, the ALT is normal and the bile acid test comes back fine, I'm happy to monitor that dog instead of investigating.
And when we already know a dog has pancreatitis or Cushing's, the liver numbers are a downstream effect of that. Treat the main problem, then recheck.
If your dog is well and the elevation is mild, I'd recheck the bloodwork in 4 to 8 weeks and add a bile acid test if it's still up. That covers most of these.
If the values are climbing across two or three tests, or your dog is actually showing symptoms, I'd move faster. Increased thirst, a change in appetite, vomiting, diarrhea, weight loss, yellow gums or a swollen belly all push this up the list. That combination is worth a same-week appointment.
And if your dog is on prednisone or phenobarbital, take a breath before you worry. It's the most common explanation I find, and the one that needs the least done about it.
If you'd like us to look at your dog's results, you can book an appointment online or call us at (519) 896-0532. Bring the actual lab report if you have it, and any older bloodwork to compare it against.
There isn't one clean cut-off, and I'd be cautious of any source that hands you a number. It depends on which enzyme is up, whether your dog has symptoms, what medications they're on, and their age and breed. A very high ALT with a sick dog concerns me far more than a higher ALP in a bright senior on no medication. Persistence is the stronger signal. An unexplained ALT still elevated after two months is the finding specialists treat as an early warning.
ALT comes mostly from liver cells and rises when those cells are damaged, which makes it the more liver-specific of the two. ALP has more sources: the liver, the bile ducts, bone, and a steroid-driven form. That gives it a lot more innocent explanations. In a growing puppy a high ALP is often just bone, and in an older dog it's often benign nodules. ALT is the one I pay closer attention to.
Not usually on their own. High liver enzymes tell me something has changed in or around the liver, not that your dog has liver disease. In a dog who feels well, the most common explanations are medication, a problem somewhere else in the body that the liver is reacting to, or benign age-related changes. What matters more than the number is whether it stays high on a recheck.
Yes, and it's expected rather than a complication. Prednisone and other steroids raise alkaline phosphatase within about 5 to 7 days of starting. Phenobarbital does the same, usually to 2 to 6 times normal. Neither means your dog has developed liver damage, and the values settle once the drug is stopped. This is one of the most common explanations I find.
Often, yes. If the cause is a medication, stopping it usually resolves them. If the cause is a problem elsewhere, like pancreatitis or Cushing's disease, treating that brings the liver values down. Plenty of mild elevations resolve on their own with no intervention at all, which is exactly why I recommend a recheck before pursuing more testing.
Don't change the diet before you know what you're treating. There's no single liver diet that suits every cause, and switching food early can muddy a recheck. If a biopsy shows copper accumulation, a copper-restricted diet becomes part of the plan and that's a specific prescription decision. Until then, keep your dog on their normal food and focus on finding the cause.
Most don't. A biopsy is the only way to diagnose chronic hepatitis properly and the only way to measure liver copper, but it sits at the end of the workup rather than the start. I'd work through a recheck, a bile acid test to assess function, screening for causes outside the liver, and an ultrasound first. If values keep climbing or function is impaired, a biopsy becomes worth discussing.
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