You’ve heard the term: Insulin resistance. You own or know of horses, such as Arabians, and Morgans, being referred to as “air ferns”. You’ve also heard people describe insulin resistance as being “just like human Type 2 diabetes”.
The comparison is easy to understand. But technically incorrect.
◆︎ For horses, it’s the insulin, not the sugar.
In type 2 diabetes, the battle is against high blood glucose. Over time, the elevated glucose levels damage the kidneys, eyes, and nerves. Lowering blood glucose is key to lowering the risk of damage to these structures.
♣ In humans: Elevated glucose, low or ineffective insulin.
In horses, we find that horses usually have normal blood glucose levels. The battle in horses is against elevated insulin levels. Elevated insulin levels can cause laminitis – even in normal horses.
♣ In horses: Normal glucose, high insulin.
◆︎ Why we cant’s use human diabetes medications
In humans with diabetes, it’s common for the physician to prescribe glipizide or injectable insulin to lower the blood sugar levels. For horses, these treatments are not appropriate.
➡ Glipizide, and drugs like it, work by telling the pancreas to secrete MORE insulin. In humans, this helps lower glucose levels. In horses with insulin resistance, they already have excessive insulin circulating in their system. Taking a drug that would increase insulin levels could cause a laminitic episode, or worsen an existing laminitic episode
➡ Insulin injections: In humans, when the pancreas is no longer secreting sufficient insulin, insulin injections become a logical choice. In horses, they already have too much insulin. This would just compound an existing problem. An injection of insulin could cause laminitis.
➡ Many herbs or supplements that can help lower glucose levels for diabetics are not helpful for horse, since the horse’s problem is elevated insulin, not elevated glucose levels.
◆︎ What can help the horse: Diet
The goal is to feed a horse in a manner that does not spike the insulin levels.
☛ Hay: Feed low sugar/starch hay (low hydrolysable carbohydrates) under 10%.
☛ Soak hay to further reduce the sugars in hay.
☛ No grain, sweet feed, or high sugar/starch treats.
The goal is to reduce the height of the insulin curve.
◆︎ What can help the horse: Metformin
Research has determined that metformin can reduce the insulin levels substantially. However, it’s been found that the blood insulin levels creep back up within a month. It appears to be effective for a short-term strategy, but not suitable for long-term control.
◆︎ What can help the horse: SGLT2 Inhibitors (the -flozin drugs)
In the last few years, SGLT2 inhibitors have become popular. They work by reducing the glucose levels through the urine. This drop in glucose prompts the horse’s pancreas to stop creating so much insulin.
Careful management is necessary with this new class of drugs. More information on the management protocol for a horse on SGLT2 inhibitors is available here.
◆︎ Take home message:
When reading about supplements or treatments that improve insulin sensitivity in the horse, it’s important to understand the mechanism behind the supplement or treatment.
Lowering blood glucose is not the goal in treating insulin resistant horses. Lowering insulin levels is the goal because that lowers the risk of laminitis.
We do the best we can for our horses. Understanding our horse's needs is a part of that.
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Disclaimer: Statements regarding dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease or health condition.
©Joan Kulifay, MSc. 2026