Earlier this month, new research carried out in collaboration with SPILLERS was presented at a leading scientific conference in the USA. This included two studies which have shed light on how the accuracy of a test commonly used to diagnose insulin dysregulation could possibly be improved in the future…


Why is this so research important?

Insulin dysregulation is associated with an increased risk of laminitis and is now considered the main feature of Equine Metabolic Syndrome (EMS). However previous research has raised some questions over the accuracy of the oral sugar test commonly used to diagnose insulin dysregulation.

The oral sugar test (OST) explained

The oral sugar test measures how much insulin the horse or pony produces in response to consuming sugar, with result above a certain level considered as ‘positive’ for insulin dysregulation. The horse or pony is fasted overnight and in some cases, a simple blood test is used to measure ‘baseline’ insulin the following morning. A ‘sugar challenge’ is then given in the form of Karo syrup administered by syringe. Glucose and insulin levels are then measured (by blood test) 60 and/ or 90 minutes after the sugar challenge.


Study 1: Does the OST dose need to be increased?

Previous research has shown that increasing the dose of Karo syrup could better differentiate between ponies with and without a history of laminitis. However the effect of dose in horses was not investigated. In this new study researchers compared the ability of the OST to diagnose insulin dysregulation in horses using different doses on Karo syrup and found that in some horses, insulin dysregulation was only identified using the higher dose. These results suggest that the current OST may not be able to effectively detect insulin dysregulation some horses.

Study 2: Does the season affect insulin response?

It has been known for some time that levels of the ACTH hormone used to diagnose PPID or ‘Cushing’s’ are naturally higher in the autumn and as a result, laboratories and vets use seasonally adjusted reference ranges when interpreting test results.  In this new study, insulin levels in response to the OST were found to be lower in the autumn, suggesting that seasonally adjusted reference ranges may also be required when testing for insulin dysregulation.


Did you know?

These two studies are just a small part of our on-going research into laminitis. We are far from having all of the answers but further work to improve our knowledge of insulin dysregulation and other risk factors for laminitis is already underway. We hope that this research will help to provide a better understanding of how laminitis can be treated and ultimately prevented in the future.


For more advice on feeding horses and ponies with insulin dysregulation contact the SPILLERS Care-Line



Macon, E. L., P. A. Harris, V. D. Barker, S. Elzinga, A. A. Adams. (2019). Insulin dysregulation and healthy horses’ seasonal insulin responses to the oral sugar test. 26th Equine Science Society Symposium, Asheville, NC, June 3 – 6 2019 Journal of Equine Veterinary Science 76 p 38

Macon, E. L., P. A. Harris, A. Herbst, A. A. Adams. (2019). Effect on the insulin response to varying doses of corn syrup to the oral sugar test (OST). 26th Equine Science Society Symposium, Asheville, NC, June 3 – 6 2019. J Equine Veterinary Science 76 p 42-43