Equine Performance Veterinary Practice
An easy keeper with a cresty neck may have more than a weight-management problem. Equine metabolic syndrome, or EMS, describes metabolic and clinical features associated with increased laminitis risk. Insulin dysregulation is its central component. Recognizing that abnormal insulin response is the problem helps explain why testing, forage selection, and follow-up matter as much as the number on a weight tape. [1]
What insulin dysregulation means
Insulin helps regulate the use and storage of nutrients after a meal. Insulin dysregulation includes excessive insulin concentrations at rest or after eating, and may include reduced tissue sensitivity to insulin. A horse can maintain a normal blood glucose concentration while producing more insulin than is healthy. This is why a normal glucose result cannot, by itself, rule out metabolic disease. [1, 2]
Prolonged high insulin can contribute to damage in the lamellae, the interlocking tissues that connect the hoof wall to the structures within the foot. This form of laminitis can develop without the dramatic systemic illness associated with some other causes. Preventing repeated insulin surges is therefore a hoof-health priority. [2]
Appearance provides clues but not a diagnosis
Regional fat deposits and difficulty losing weight are common, but some lean horses have insulin dysregulation and some overweight horses do not. Breed and genetic background influence susceptibility, while diet and activity affect how that susceptibility is expressed. PPID and insulin dysregulation can coexist, particularly in older horses, so testing for one condition does not automatically exclude the other. [3]
What testing can tell us
A resting insulin measurement is useful, but a normal result may miss an excessive response to food. An oral sugar or glucose test provides a standardized carbohydrate challenge followed by timed blood samples. The question is how much insulin the horse releases in response, not simply whether sugar enters the bloodstream. [2]
Follow the clinic’s preparation instructions exactly. Feeding conditions, pain, stress, the laboratory method, and the test protocol affect interpretation. Results from different protocols should not be compared as though they were interchangeable. Repeat testing helps determine whether a management change has improved insulin control, even if the horse looks slimmer. [1, 2]
Build the diet around measured forage
Hay should be selected from an analysis rather than its color, maturity, or description as grass hay. Sugar and starch content can vary between batches. Weigh daily portions; flakes are not consistent units. For an overweight horse, calories need to be reduced gradually while preserving adequate forage, protein, vitamins, and minerals. A lean horse may need additional calories from suitable fiber or fat sources without a large sugar or starch load. [3]
Pasture can be a substantial and variable carbohydrate source. Some horses can use a grazing muzzle within a monitored plan; those with severe insulin dysregulation may require a grass-free turnout area. Short turnout is not always sufficient protection because intake can be rapid. Hay soaking may reduce soluble sugars, but the response varies, and soaking also removes other nutrients. It cannot guarantee that a particular hay is suitable. [1, 3]
Avoid severe feed restriction or prolonged food deprivation. Track body condition and weight trends, and adjust the plan with your veterinarian. The feeding program should be practical enough to sustain while preventing nutritional deficiencies. [2]
Exercise and medication have distinct roles
Regular exercise can support insulin sensitivity and weight control when the feet are comfortable and the horse is cleared for work. Active laminitis changes the priority: protect the feet and control pain rather than walking the horse to burn calories. [4]
Metformin may help blunt the insulin rise after eating in selected horses, although absorption is poor and response is variable. Levothyroxine is sometimes used temporarily to support weight loss in resistant cases; this does not mean the horse has an underactive thyroid. Neither medication replaces a carefully designed diet. [2, 4]
SGLT2 inhibitors are another option for selected horses with severe insulin dysregulation or insulin-associated laminitis. They increase glucose loss through urine and can lower insulin concentrations. Their use requires close veterinary oversight, including monitoring triglycerides and liver enzymes, as well as appetite and the insulin response. These are prescription decisions based on the individual case. [1]
Measure success beyond weight loss
A useful review includes insulin testing, body condition, feeding records, and hoof comfort. New reluctance to turn, a shortened stride, shifting weight, or increased digital pulses should prompt a call about possible laminitis rather than an increase in exercise. [2]
Contact Equine Performance Veterinary Practice for metabolic testing and a feeding plan tailored to your horse. The aim is durable insulin control and comfortable feet, with follow-up that shows whether the plan is working.
Sources and further reading
[1] Equine Endocrinology Group — 2024 EMS and insulin dysregulation recommendations
[2] ECEIM consensus statement on equine metabolic syndrome
[3] UC Davis Center for Equine Health — Equine Metabolic Syndrome
[4] Utah State University Extension — Managing Equine Metabolic Syndrome
This information does not replace veterinary advice for your individual horse.