Home / Health / Conditions / Addison's Disease
Body system: Hormones and metabolism. One of the core guides in our dog health conditions library. If your dog has worrying signs right now, start with our symptom triage guides.
Addison's disease, vets' name hypoadrenocorticism, is failure of the adrenal glands to make enough of their two essential hormone families. Cortisol, the glucocorticoid, is needed for stress response, blood sugar, gut function and normal energy. Aldosterone, the mineralocorticoid, governs sodium and potassium: it holds sodium and water in the body and excretes potassium. Lose both, which is the typical form of Addison's, and the dog cannot maintain blood pressure, blood sugar or safe potassium levels, especially under stress. It is the exact mirror image of Cushing's disease, and considerably less common.
The disease earns its nickname, the great pretender, honestly. Its signs are vague, common to dozens of conditions, and characteristically wax and wane: a dog has a few flat, off food days with a soft stool, seems to recover, then relapses weeks later. Many dogs are only diagnosed when the slow failure tips into an Addisonian crisis: collapse, shock, a dangerously high potassium that threatens the heart, low blood sugar and severe dehydration, arriving as an emergency in a dog that may have looked merely unwell that morning. The usual cause in dogs is immune mediated destruction of the adrenal cortex, suspected to have an inherited component in predisposed breeds. Rarer causes include destruction by tumor spread, bleeding into the glands, infection, and drugs used to treat Cushing's disease overshooting their target. A less common atypical form lacks the mineralocorticoid failure at first, with normal electrolytes, and is even easier to miss.
Primary Addison's is failure of the glands themselves, usually by immune mediated destruction of the adrenal cortex, with genetic predisposition in several breeds. Secondary Addison's, failure of the pituitary signal ACTH, is rare in dogs and spares aldosterone, because aldosterone is controlled mainly by potassium and blood pressure systems rather than ACTH. Sudden withdrawal after long term high dose steroid treatment can mimic the glucocorticoid side temporarily, because the dog's own system has been suppressed. Crisis triggers are the stresses a normal adrenal gland would answer with a cortisol surge: another illness, trauma, anesthesia, or even excitement and travel.
Breeds and dogs at higher risk: Addison's can affect any dog, most often young to middle aged adults, and females somewhat more than males. Breeds overrepresented include Standard Poodles, Nova Scotia Duck Tolling Retrievers, Great Danes, West Highland White Terriers, Bearded Collies and Portuguese Water Dogs, and inheritance is documented in Standard Poodles and Tollers.
Suspicion grows from the pattern plus routine bloodwork: the classic electrolyte fingerprint is low sodium and high potassium, with a sodium to potassium ratio below the normal range, alongside a lack of the expected stress pattern in the white cell count, sometimes low blood sugar and mildly raised calcium or kidney values that normalize with fluids (a notorious mimic of kidney failure). A resting cortisol measurement is a powerful screen: a value above 2 micrograms per deciliter effectively rules Addison's out. Confirmation is the ACTH stimulation test: cortisol is measured before and after a dose of the pituitary hormone, and an Addison's dog shows little or no rise, the flatline result. Dogs in crisis are stabilized with emergency fluids first, with the test run as treatment begins, because waiting for results while a high potassium threatens the heart is the wrong order.
A crisis is treated as the emergency it is: aggressive intravenous fluids to restore circulation and dilute potassium, correction of blood sugar, and glucocorticoid replacement once the diagnostic sample is drawn, followed by mineralocorticoid replacement as the dog stabilizes. Most crisis dogs improve strikingly within a day or two. Long term, both missing hormones are replaced for life: mineralocorticoid either as a monthly injection of desoxycorticosterone pivalate (DOCP) or as daily oral fludrocortisone, plus a daily low dose glucocorticoid, usually prednisone, with extra glucocorticoid cover doubled or so around predictable stresses, surgery and illness, on your vet's instructions. Electrolytes are rechecked after starting and after dose changes, then periodically for life.
With replacement in place, the prognosis is excellent, one of the best in chronic medicine: treated dogs are expected to live normal lifespans with normal energy. The failures are almost all failures of detection, a crisis in an undiagnosed dog, or of interruption, replacement stopped because the dog seemed cured. The hormones are not a course to finish; they are a substitute for glands that will not recover.
Build the routine around never running out: order medication early, keep a small reserve, and carry a written summary of the diagnosis and doses for kennels, sitters and any emergency clinic, because an Addison's dog that cannot take its medication during another illness needs veterinary cover quickly. Warn every vet who treats your dog, including for dentistry and surgery, so stress dose planning happens in advance. Keep a simple log of appetite, energy and any collapsing or shaking episodes to bring to rechecks. Owners often say the dog they get back on treatment is the dog from a year ago; keep that dog by keeping the routine boring.
See also: symptom triage guides | All conditions A-Z | Health hub
No. The adrenal glands do not recover, so replacement hormones are lifelong. The encouraging part is how completely replacement works: treated dogs typically have normal energy and a normal lifespan.
The acute collapse that occurs when cortisol and aldosterone deficiency overwhelms the body, often triggered by stress: shock, severe dehydration, high potassium that can disturb the heart, and low blood sugar. It is a true emergency, treated with intravenous fluids and hormone replacement.
Screening bloodwork often shows low sodium and high potassium. A resting cortisol above 2 micrograms per deciliter rules it out. The confirming test is the ACTH stimulation test, where an Addison's dog's cortisol barely rises after stimulation.
Because its signs are vague, intermittent and shared with gut, kidney and general illness: tiredness, picky appetite, vomiting and diarrhea that come and go. It is missed for months in some dogs and is classically diagnosed at the moment of crisis.
Two replacements: a mineralocorticoid, either a monthly DOCP injection or daily fludrocortisone tablets, and a daily glucocorticoid, usually low dose prednisone, increased temporarily around stress, illness or surgery as your vet directs.
This page is general information drawn from the published guidance of the organizations listed under Sources below. It is not veterinary advice, and it does not replace your own veterinarian, who knows your dog. If your dog may have eaten something toxic, contact your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 straight away. A consultation fee may apply on the helplines. If your dog is struggling to breathe, has collapsed, is having a seizure that will not stop, or has a swollen belly with retching that brings nothing up, go to an emergency veterinarian now and do not wait to finish reading.
Last updated: November 2026. Facts on this page were checked against the sources listed above. How we work: our methodology.