High Liver Enzymes in Dogs: ALT, AST, ALP Causes and Next Steps
High ALT indicates liver cell damage or stress, often caused by medications, infections, or liver disease. Normal range: 10-125 U/L.
If your dog's bloodwork shows a high ALT value, it's natural to feel concerned. This guide explains what ALT is, why it rises, and what it means for your dog's health.
What is ALT in Dogs?
ALT (Alanine Aminotransferase) is an enzyme found primarily in the liver. When liver cells are irritated, inflamed, or damaged, ALT leaks into the bloodstream, causing elevated levels on blood tests.
Normal Range:
Approximately 10–125 U/L (varies by laboratory)
Why ALT Matters
High ALT signals liver stress, but it doesn't automatically mean liver failure or severe disease. Context is crucial — the degree of elevation, other lab values, and your dog's clinical signs all matter.
ALT Severity Chart: Understanding Your Dog's Results
| ALT Level (U/L) | Severity | What It Means | Typical Action |
|---|---|---|---|
| 10-125 | Normal | Liver enzymes within healthy range | Routine monitoring as part of wellness exams |
| 126-300 | Mild | Often medication-related, stress, or temporary inflammation | Recheck in 2-4 weeks, review medications, monitor symptoms |
| 301-600 | Moderate | Significant liver stress, possible hepatitis or toxin exposure | Additional testing (bile acids, ultrasound), identify cause, consider treatment |
| Over 600 | Severe | Serious liver damage, toxin ingestion, or acute hepatitis | Immediate comprehensive workup, aggressive treatment, possible hospitalization |
Important Note:
The severity of ALT elevation must be interpreted alongside your dog's symptoms, other bloodwork values, and medical history. A dog with ALT of 150 showing jaundice needs more urgent attention than a dog with ALT of 400 who feels completely normal.
Common Causes of High ALT in Dogs
- Medications: NSAIDs (Rimadyl/Carprofen), steroids (prednisone), Apoquel, phenobarbital
- Infections: Viral hepatitis, leptospirosis, bacterial infections
- Toxins & Diet: High-fat foods, xylitol, certain mushrooms, algae toxins
- Chronic Conditions: Cushing's disease, diabetes, chronic hepatitis, liver disease
- Other Causes: Cancer, age-related changes, breed predispositions
Want to see if your dog's ALT has been rising over time?
Upload lab results to VetLens and get instant graphs and explanations showing trends in your dog's liver values.
Try VetLens FreeSymptoms Pet Owners Might Notice
Dogs with elevated ALT may show:
- • Lethargy or decreased activity
- • Loss of appetite
- • Vomiting or diarrhea
- • Excessive drinking and urination
- • Yellow discoloration of eyes or gums (jaundice)
- • Abdominal discomfort or swelling
Note: Many dogs with mildly elevated ALT show no symptoms at all.
What Happens Next?
Your veterinarian may recommend:
- • Rechecking bloodwork in 2–4 weeks to see if values normalize
- • Additional liver tests (bile acids, GGT, bilirubin)
- • Abdominal ultrasound to visualize liver structure
- • Medication review if your dog takes drugs that affect the liver
- • Dietary changes to support liver health
- • Supplements like SAMe or milk thistle
Key Takeaway:
High ALT indicates liver cell stress but doesn't always mean serious disease. Trends over time and other lab results matter most for determining significance and treatment approach.
Related Reading
- • Dog High ALP Bloodwork – another important liver enzyme that often rises alongside ALT
- • Cat Liver Enzymes Explained – understanding ALT, ALP, AST, and GGT in feline patients
- • Anemia in Dogs – liver disease can affect red blood cell production
Want ALT Explained for Your Dog?
Upload your dog's bloodwork into VetLens and get:
- ✓ A plain-English breakdown of ALT and related values
- ✓ Context based on breed, age, and medical history
- ✓ Suggested questions to ask your vet
- ✓ Tailored diet and supplement advice
Frequently Asked Questions
Is high ALT always serious?
No. Mild increases (up to 2-3 times normal) are often medication- or age-related and may resolve on their own.
Can medications raise ALT?
Yes, especially pain relievers like carprofen, steroids like prednisone, and allergy medications like Apoquel.
How do you lower ALT?
Treatment focuses on addressing the underlying cause — adjusting medications, treating infections, or providing liver-supportive diet and supplements.
What is a normal ALT level?
Normal ranges are typically 10–125 U/L, though this varies by laboratory and testing method.