Iron Poisoning (Hemachromatosis) in Horses

Key Takeaways

Iron poisoning is a potentially life-threatening condition that occurs when there is an excess of iron in a horse's system. 

• Iron toxicosis can be either acute, typically caused by an overdose of iron-containing supplements, or chronic, caused by excessive accumulation of iron in the system for an extended length of time

• Common symptoms of acute iron toxicosis include abdominal pain, reduced appetite, diarrhea, and yellow gums

• Diagnosis is based on history of exposure, physical examination, bloodwork, and measuring iron levels in the bloodstream

• Once diagnosed, early treatment focuses on stabilization with IV fluids and removing any undigested iron-containing material from the stomach

• Once stabilized, treatment involves chelation therapy to bind and remove iron in the bloodstream

• Prognosis depends on the kind of toxicosis, timing of treatment, and the extent of organ damage

A Closer Look: What is Iron Poisoning in Horses?

Iron is a micronutrient essential to maintaining healthy levels of hemoglobin in the blood. Hemoglobin is the primary functional protein in blood that carries oxygen from the lungs to the body tissues. If the concentration of iron in the blood exceeds levels needed for normal functioning, it can lead to iron poisoning. 

Symptoms of iron toxicosis vary in accordance with the underlying cause. It can be further characterized as acute or chronic. 

Acute iron toxicosis: is typically caused by excessive ingestion of iron-containing supplements. Symptoms include:

Reduced appetite • Lethargy • Excessive bleeding  

Yellow discoloration of the eyes, gums and skin (jaundice)

Red spots on the gums • Behavioral changes

Left untreated, acute iron toxicosis ultimately leads to liver failure and accumulation of ammonia in the bloodstream due to impaired liver function. Symptoms of ammonia accumulation (hepatic encephalopathy) include:

Uncoordinated movement (ataxia) • Circling

• Head pressing • Loss of consciousness

Chronic iron toxicosis: also known as hemochromatosis, is a condition in which the animal's body absorbs and stores excessive amounts of iron. Symptoms include: 

• Weight loss • Rough hair coat

• Lethargy • Appetite loss

Risk Factors

Iron toxicosis is rare in horses. In both its acute and chronic form, iron toxicosis is a potentially life-threatening condition warranting prompt veterinary attention.

If iron over-supplementation is suspected, immediate veterinary attention is crucial in ensuring a favorable prognosis. 

Foals are more susceptible to over-supplementation due to their lower body weight, which makes the toxic dose of iron much smaller than in adult horses. Horses given iron supplements are more likely to develop iron toxicosis.

Possible Causes

Causes of iron toxicosis include:

• Overdose of iron supplements and multivitamin

• Ingestion of excessive iron from water sources

Main Symptoms

Common symptoms of iron toxicosis include: 

Abdominal pain (colic) 

• Weight loss 

Reduced appetite 


• Blood in the stool

Testing and Diagnosis

A horse presenting symptoms associated with iron toxicosis generally undergoes the following diagnostics:  

• Physical exam 

• Blood tests, including testing for iron levels

• History of supplement use or water quality testing

Steps to Recovery

Initial treatment is focused on stabilization. Supportive care involves:

• Fluid therapy and electrolytes: to ensure adequate hydration

• Medications to protect the intestinal lining

• Stomach lavage to remove any undigested supplement

Symptomatic treatment of iron toxicosis involves: 

• Chelation therapy: chelating agents bind to excess iron in the system and help its excretion from the body

Currently, there is definitive treatment for chronic iron toxicosis. Removing the source of iron and monitoring for changes in liver and cardiac function are recommended in these cases. 

Prognosis for iron toxicosis varies widely, in accordance with the underlying cause, the timing of treatment, and the extent of organ damage. 

Acute iron toxicosis carries a good prognosis if promptly treated in the initial stages. If medical attention is delayed or the condition is left untreated, it can lead to permanent and life-threatening liver damage. 

In both acute and chronic iron toxicosis, horses that develop symptoms of hepatic encephalopathy have a poor prognosis, and many are euthanized.


Iron toxicosis is not contagious. 

Acute iron toxicosis is preventable by ensuring that horses cannot access iron sources. Strategies include:

• Administration of Vitamin E and selenium supplements, which can help prevent iron toxicosis 

• Analyzing iron content in water supplies 

• Discussing supplements with a veterinarian prior to administration 

• Only administering additional iron to horses who have a confirmed iron deficiency

Is Iron Poisoning Common in Horses?

Iron toxicosis is a rare condition in horses.

Typical Treatment

• Fluid therapy 

• Electrolytes

• Gastroprotectants 

• Gastrointestinal decontamination 

• Chelation therapy

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