Insulin Resistance (IR) in Horses: What It Is and How to Manage It

by Cookie Root

Insulin resistance in horses is a growing concern, especially for easy keepers, overweight horses, and those prone to laminitis. If your horse has a cresty neck or struggles with weight gain, it’s essential to understand equine metabolic disorders and how they impact long-term health.

While both Cushing's disease and Insulin Resistance (IR) can affect horses and share some symptoms, the key difference is that Cushing's is a hormonal disorder caused by a tumor in the pituitary gland, leading to excessive cortisol production, while IR is a metabolic condition where the body becomes resistant to the effects of insulin, causing high blood sugar levels; essentially, Cushing's is a disease with a specific underlying cause, while IR is a physiological response to dietary factors that can be managed through diet changes.

Let’s break down what insulin resistance is, how to identify IR in horses, and the best strategies for managing insulin-resistant horses through proper diet, exercise, and veterinary care.

What Is Insulin Resistance in Horses? In a healthy horse, insulin regulates blood sugar levels by moving glucose from the bloodstream into cells for energy. However, in horses with insulin resistance, the cells don’t respond properly, leading to high blood sugar and insulin levels. This can result in:

✔️ Equine obesity and difficulty losing weight ✔️ Fat deposits on the neck, shoulders, and tailhead ✔️ Chronic laminitis or sore hooves ✔️ Lethargy and reduced performance

If your horse shows these symptoms, testing for insulin resistance can help confirm a diagnosis and guide a management plan.

Case Study: How One Mare Overcame IR A case was published in the Arquivo Brasileiro de Medicina Veterinária e Zootecnia featured a Colombian Creole mare diagnosed with Equine Metabolic Syndrome (EMS), a condition closely linked to insulin resistance in horses. Here is a brief summary . . .

The Problem The mare was gaining weight rapidly, developing a hard, cresty neck, and experiencing recurrent laminitis.

Getting a Diagnosis Her veterinarian performed a combined glucose-insulin test, revealing elevated insulin levels and confirming equine insulin dysregulation.

The Management Plan

• 🔹 Low-starch, high-fiber diet – Grain was removed, and she was switched to low-NSC hay soaked to reduce sugar content.
• 🔹 Structured exercise routine – She started with hand-walking and groundwork before returning to light riding.
• 🔹 Regular metabolic testing – Her insulin and glucose levels were monitored to track progress.

The Results: Within six months, the mare successfully lost excess weight, her laminitis symptoms significantly improved, and she returned to light work without complications. While this is just one case, it highlights the positive outcomes that can be achieved with proper management and care.

Final Thoughts on Insulin Resistance in Horses If you are managing a horse with IR, a veterinarian should help build a personalized plan. Core strategies include dietary management, exercise, weight management, medical management, monitoring and bloodwork. Our veterinarians at Oakhurst Equine Veterinary Services are here to help you if you are unsure. Contact us for an appointment or consultation. Early detection is key to preventing complications like laminitis and equine metabolic syndrome. By taking a proactive approach, you can help your insulin-resistant horse live a happy, healthy life.

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