Liver Disease in Horses: Signs, Causes, and When to Call Your Vet

Quick Answer
  • Liver disease in horses can be mild and slow-moving or sudden and life-threatening, depending on the cause and how much liver function is affected.
  • Common warning signs include poor appetite, weight loss, jaundice, behavior changes, aimless wandering, head pressing, and sun-sensitive skin lesions on unpigmented areas.
  • Toxic plants such as ragwort and other pyrrolizidine alkaloid-containing weeds, infections, bile duct inflammation, and post-serum hepatitis (Theiler disease) are important causes.
  • Call your vet promptly for yellow gums or eyes, new neurologic signs, marked lethargy, or skin crusting after sun exposure. These can signal liver failure or hepatic encephalopathy.
  • Typical diagnostic cost range in the US is about $300-$900 for an exam and bloodwork, with ultrasound and biopsy potentially increasing the total to roughly $1,200-$3,500+.
Estimated cost: $300–$3,500

What Is Liver Disease in Horses?

Liver disease in horses is a broad term for conditions that damage the liver or reduce how well it works. The liver helps process nutrients, clear toxins, support digestion through bile production, and make important proteins. Because it has a large reserve capacity, a horse may have significant liver injury before obvious signs appear.

Some horses develop chronic liver disease over weeks to months, while others become sick much faster with acute hepatitis or liver failure. When the liver can no longer clear toxins effectively, those toxins can affect the brain and nervous system. This is called hepatic encephalopathy, and it can cause behavior changes, wandering, weakness, or seizures.

Liver disease is not one single diagnosis. It is a clinical problem with many possible causes, including toxic plants, infectious disease, bile duct inflammation, and reactions linked to equine-origin biologic products such as plasma or tetanus antitoxin in some cases. Your vet usually needs bloodwork, and sometimes ultrasound or biopsy, to sort out which type of liver disease your horse has and how serious it is.

Symptoms of Liver Disease in Horses

  • Poor appetite or reduced interest in feed
  • Weight loss or poor body condition
  • Lethargy or reduced performance
  • Jaundice (yellow gums, sclera, or skin)
  • Photosensitization
  • Behavior changes or depression
  • Aimless wandering, head pressing, circling, or ataxia
  • Blindness, seizures, or collapse

Some horses with liver disease look only mildly off at first. Others show dramatic neurologic signs once liver function drops enough for toxins to build up. Skin lesions on white or lightly pigmented areas after sun exposure are another important clue, especially when paired with weight loss or jaundice.

See your vet immediately if your horse has yellow eyes or gums, sudden behavior changes, stumbling, head pressing, seizures, or severe sun-related skin injury. Those signs can point to advanced liver dysfunction and should not be monitored at home without veterinary guidance.

What Causes Liver Disease in Horses?

One of the best-known causes is toxic plant exposure, especially plants that contain pyrrolizidine alkaloids. These include ragwort and several related weeds. Horses may eat them when pasture is poor, during drought, or when dried plant material is mixed into hay. The liver damage can be delayed, so a horse may become sick long after the original exposure.

Other causes include ascending cholangiohepatitis or other inflammatory conditions involving the liver and bile ducts, as well as infectious causes of hepatitis. In adult horses, Theiler disease is an important cause of acute hepatitis and liver failure. It has been linked to equine-origin biologic products such as tetanus antitoxin or plasma, often with signs developing about 4 to 10 weeks later, although not every case has a known product exposure.

Less commonly, congenital vascular problems such as portosystemic shunts can affect foals, and some horses may have liver involvement from tumors or other systemic illness. Because the list of causes is broad, your vet will usually look at your horse's age, diet, pasture access, medication and biologic history, travel, and timing of signs before recommending the next tests.

How Is Liver Disease in Horses Diagnosed?

Diagnosis usually starts with a physical exam and bloodwork. Your vet may run a CBC and chemistry panel to look for changes in liver-associated enzymes and liver function markers. In horses, tests such as GGT, SDH, GLDH, AST, bilirubin, and bile acids are commonly used to assess liver injury and function over time.

Bloodwork can strongly suggest liver disease, but it does not always reveal the exact cause. That is why your vet may also recommend abdominal ultrasound to evaluate liver size, texture, and nearby structures. If your horse has neurologic signs, your vet may also assess for hepatic encephalopathy and check for other problems that can look similar.

In many cases, a liver biopsy is the most useful way to confirm the diagnosis, estimate how much damage is present, and help guide prognosis. Before biopsy, your vet may check clotting ability because the liver makes proteins involved in normal blood clotting. Serial blood tests are often just as important as the first set, since trends can help show whether the liver is stabilizing, worsening, or responding to treatment.

Treatment Options for Liver Disease in Horses

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$400–$1,200
Best for: Stable horses with mild signs, pet parents needing a lower-cost starting plan, or cases where your vet suspects chronic toxic exposure and the horse is still eating and neurologically normal.
  • Farm call or clinic exam
  • Baseline bloodwork with liver values
  • Removal from suspected toxic pasture or hay source
  • Strict sun protection for horses with photosensitization
  • Diet changes directed by your vet, often with careful protein management and highly palatable forage
  • Short-interval recheck bloodwork
Expected outcome: Variable. Some horses improve if the cause is removed early and enough healthy liver remains. Chronic scarring or neurologic signs make the outlook more guarded.
Consider: This tier can identify many cases and support recovery, but it may not define the exact cause. Without imaging or biopsy, prognosis is less precise and important complications may be missed.
Most Common

Recommended Standard Treatment

$1,200–$3,500
Best for: Most horses with confirmed or strongly suspected liver disease, especially those with jaundice, weight loss, persistent abnormal bloodwork, or unclear cause.
  • Complete exam and repeat chemistry/CBC testing
  • Bile acids and bilirubin assessment
  • Abdominal ultrasound
  • Targeted medications and supportive care chosen by your vet
  • Hospital or day-treatment fluids when needed
  • Nutritional support and management of hepatic encephalopathy risk
  • Possible liver biopsy if clotting status and case stability allow
Expected outcome: Fair to guarded depending on the cause, severity, and whether the horse has neurologic signs. Horses with treatable inflammation or early toxic injury may do well, while advanced fibrosis or acute liver failure carries more risk.
Consider: This approach gives better diagnostic clarity and a more tailored plan, but it requires more testing and a higher upfront cost range.

Advanced / Critical Care

$3,500–$10,000
Best for: Horses with acute hepatitis, severe jaundice, inability to maintain hydration, marked neurologic signs, or cases needing referral-level diagnostics and monitoring.
  • Referral hospital care or ICU-level monitoring
  • Continuous IV fluids and electrolyte support
  • Frequent bloodwork to track liver function and complications
  • Aggressive management of hepatic encephalopathy and neurologic signs
  • Ultrasound-guided biopsy or advanced imaging when appropriate
  • Tube feeding or intensive nutritional support in selected cases
  • Management of severe photosensitization wounds or secondary complications
Expected outcome: Guarded to poor in horses with severe hepatic encephalopathy or fulminant liver failure, though some acute cases recover with intensive support if enough liver function remains.
Consider: This tier offers the closest monitoring and the broadest diagnostic options, but it is resource-intensive and not every horse is a candidate for referral or invasive testing.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Liver Disease in Horses

Bring these questions to your vet appointment to get the most out of your visit.

  1. Which bloodwork changes suggest liver injury versus reduced liver function in my horse?
  2. Based on my horse's history, do you think toxic plants, infection, bile duct disease, or Theiler disease is most likely?
  3. Does my horse need bile acids testing, ultrasound, or a liver biopsy right now?
  4. Are there any feeds, supplements, medications, or pasture plants I should stop immediately?
  5. Is my horse showing any signs of hepatic encephalopathy or risk for neurologic complications?
  6. What level of sun protection is needed if my horse has photosensitization?
  7. What should I monitor at home each day, and which changes mean I should call you right away?
  8. What is the expected cost range for the next step in diagnosis or treatment?

How to Prevent Liver Disease in Horses

Prevention starts with pasture and hay management. Walk fields regularly and remove toxic weeds when possible, especially ragwort and other plants known to contain pyrrolizidine alkaloids. Good forage availability matters. Horses are more likely to sample harmful plants when pasture is sparse, overgrazed, or drought-stressed. Check hay quality carefully, because dried toxic plants may be harder to spot and may still be dangerous.

It also helps to keep a clear medical record for each horse, including vaccines, plasma products, tetanus antitoxin, supplements, and recent medications. If your horse receives an equine-origin biologic product, ask your vet what signs to watch for over the following weeks. Not every horse exposed will become ill, but early recognition matters.

Routine wellness exams and bloodwork can be useful for horses with previous liver disease, chronic weight loss, unexplained poor performance, or ongoing exposure concerns. Prevention is not about one perfect step. It is about lowering risk, catching problems earlier, and working with your vet when something changes.

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