Why does your horse need a blood test 4-6 weeks after starting medication to treat Equine Cushing’s disease?

Horses with untreated or uncontrolled Equine Cushing’s disease are at a high risk of developing signs associated with this disease such as laminitis, repeated infections, muscle wastage, lethargy, poor coat quality, and increased drinking and urination…. so it’s important to ensure that the treatment you are administering is working and controlling this disease.


When a horse or pony has Equine Cushing’s disease the pituitary gland at the base of their brain produces too many hormones. These high hormone levels are the cause of the symptoms associated with this disease.

The aim of treating Cushing’s is to reduce these hormones to more normal levels so that the symptoms of disease stop. The problem is that hormones can hang around in the body for a long time, and they can have a long-lasting effect on some tissues in the body. This means that even when the pituitary gland stops producing high levels of hormones, the symptoms of disease don’t stop immediately. In addition to this there is some variation in how long individual horses take to respond to treatment.

A blood test is therefore always recommended 4-6 weeks after starting treatment for Equine Cushing’s disease because it is difficult to know from the symptoms alone whether the disease is under control.   Your horse is at risk of developing symptoms if the disease is not under control.

The blood test checks the levels of a hormone called ACTH: in most cases the test will show that your horse’s ACTH level has successfully reduced to below the reference range for that time of year. If this is the case your vet will usually leave your medication dose the same, and may suggest some additional management strategies to address any ongoing clinical signs or risk factors.

In some cases the ACTH level may not have reduced enough and will still be above the reference range for that time of year. If this is the case your vet is likely to suggest adjusting the dose of medication with further testing every 4-6 weeks until your horse is stable with their Cushing’s under control.

You can read more about other horse owners experience of caring for a horse with Equine Cushing’s disease by joining our community at www.careaboutcushings.co.uk, where we also provide an annual free* monitoring test for Equine Cushing’s disease for our members.

*free basal ACTH laboratory fees only from. Visit, blood sampling and interpretation fees may be applied by your veterinary practice.