Addison's disease happens when the adrenal glands don't make enough of their hormones, usually both cortisol and aldosterone. Vets also call it hypoadrenocorticism.1,2 It's uncommon, but it's known as "the great pretender" because its vague signs mimic many other, more common problems.3 Left untreated it can cause a life-threatening crisis, yet with lifelong treatment most dogs do very well.1,4 This guide covers the signs, the adrenal crisis, breeds at risk, atypical Addison's, diagnosis and treatment.
Go to a vet or emergency clinic now if your dog:
- Collapses, is very weak, or has a slow or irregular heartbeat1,4
- Has severe vomiting or diarrhea, especially with weakness or collapse4
- Has known Addison's and becomes ill, stops eating or misses medication1
An adrenal crisis (sometimes called an Addisonian crisis) is an emergency.2,4
What the Research Shows
- It's uncommon. Among 905,543 UK dogs, 0.06% had an Addison's diagnosis in a year.5
- Standard Poodles are at very high risk. They had 51 times the odds of crossbreeds; Labradoodles and West Highland White Terriers were also at higher risk.5
- It strikes younger dogs. The median age at diagnosis was about 5 years.5,6
- One blood test can rule it out. In one study, every dog with Addison's had a resting cortisol of 2 µg/dL or less, so a higher result makes it very unlikely.7
- Normal electrolytes don't rule it out. In two referral studies, about 1 in 5 dogs had normal sodium and potassium at diagnosis.8,6
What Is Addison's Disease?
Most cases are primary Addison's, in which the dog's immune system is thought to destroy the outer layer of the adrenal glands.1 In this disease, low cortisol can cause low blood sugar and low blood pressure, and low aldosterone causes high potassium and low sodium.1 Addison's can also follow treatment for Cushing's disease or sudden withdrawal of long-term steroid medicine.4 See adrenal gland problems in dogs.
Signs of Addison's Disease in Dogs
- Lethargy (77% of confirmed cases in the UK study)5
- Poor appetite (73%) and vomiting (73%)5
- Diarrhea (46%) and weight loss (29%)5
- Shaking or trembling, and increased thirst and urination in some dogs4
Signs often come and go, and may get worse with stress such as boarding or travel.3 Many dogs improve temporarily with fluids or steroids given for another suspected problem, which can delay the diagnosis.4
Adrenal (Addisonian) Crisis
Some dogs are first diagnosed when they collapse in shock. Low cortisol and high potassium can cause severe weakness, dehydration, low blood pressure and a dangerously slow or irregular heartbeat.1 These dogs need emergency intravenous fluids and hormone treatment; in the UK study, 76% of dogs received initial IV fluids.5 With prompt treatment, most dogs recover, even after a crisis.4,6
Which Dogs Get Addison's?
Addison's usually affects young to middle-aged dogs.1,5 In the UK study, neutered dogs had 2.5 times the odds of entire dogs, but sex itself made no difference.5 Breeds at higher risk include the Standard Poodle, Nova Scotia Duck Tolling Retriever, Portuguese Water Dog, Bearded Collie, Great Dane, Leonberger and West Highland White Terrier.1,4,5
Atypical Addison's
Some dogs lack cortisol but still make enough aldosterone, so their sodium and potassium are normal. This used to be called "atypical" Addison's.2,9 It was recorded in about 6% of UK cases, but about 20% of dogs in two referral studies had normal electrolytes, so it may be underdiagnosed.5,8,6,1 These dogs are often older and less likely to vomit, and more than half of those checked had, or later developed, aldosterone deficiency too.8
How Vets Diagnose Addison's
- Routine blood tests often show high potassium and low sodium, but these can be normal and can also occur with other diseases.1,8
- Resting (baseline) cortisol: a result above 2 µg/dL effectively rules out Addison's. A low result isn't enough to diagnose it.7,1
- ACTH stimulation test: the test that confirms the diagnosis.1,3 In the UK study, 59% of cases had no ACTH test recorded, so some may have been diagnosed on less certain evidence.5
Steroid medicines given before testing can interfere with results, so tell your vet about any recent treatment.
Treatment of Addison's Disease
- Mineralocorticoid replacement to replace aldosterone: either injections of desoxycorticosterone pivalate (DOCP), sold as Percorten-V (FDA-approved 1998) and Zycortal (2016), or a daily fludrocortisone tablet.10,1
- Glucocorticoid replacement, usually a low daily dose of prednisolone or prednisone, increased during illness or stress as your vet directs.1,4
- Regular blood tests to check electrolytes and adjust treatment.1
In UK practices, most dogs were treated with DOCP plus prednisolone.5 Treatment is lifelong.11 Never stop or skip medication without talking to your vet.
Outlook
With treatment and monitoring, the long-term outlook is good.1,4 In a study of 205 treated dogs, median survival after diagnosis was 4.7 years, and more than 80% of dogs had a good to excellent response to treatment.12
Frequently Asked Questions
What are the first signs of Addison's disease in dogs?
Low energy, poor appetite, vomiting, diarrhea and weight loss that come and go.
Why is Addison's called "the great pretender"?
Its vague signs look like many more common problems, such as stomach upsets or kidney disease.
What breeds get Addison's disease?
Standard Poodles, Nova Scotia Duck Tolling Retrievers, Portuguese Water Dogs, Bearded Collies, Great Danes and West Highland White Terriers, among others.
How is Addison's disease diagnosed?
A resting cortisol test can rule it out, and an ACTH stimulation test confirms it.
What is an Addisonian crisis?
A sudden collapse from very low adrenal hormones. It's an emergency that needs IV fluids and hormones.
Can dogs live a normal life with Addison's?
Yes. With lifelong treatment and regular blood tests, most dogs do very well.
What is atypical Addison's?
Addison's with normal sodium and potassium, because only cortisol is lacking. Some of these dogs later lose aldosterone too.
Is Addison's disease painful for dogs?
The illness causes weakness, nausea and sometimes stomach upset. Once treated, dogs usually feel normal.
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Sources and further reading
This article was rewritten and fact-checked on October 15, 2026 against current veterinary references and specialist guidelines:
- Van Vertloo L. Addison disease (hypoadrenocorticism) in animals. Merck Veterinary Manual, July 2024.
- Niessen SJM, Behrend EN, Fracassi F, et al. Agreeing Language in Veterinary Endocrinology (ALIVE): Cushing's syndrome and hypoadrenocorticism. Veterinary Sciences, 2025.
- Bellefontaine J. The great pretender: understanding Addison's disease in dogs. University of Illinois College of Veterinary Medicine, March 2026.
- Hunter T, Williams K, Ward E, Downing R. Addison's disease in dogs. VCA Animal Hospitals, 2023.
- Schofield I, Woolhead V, Johnson A, Brodbelt DC, Church DB, O'Neill DG. Hypoadrenocorticism in dogs under UK primary veterinary care: frequency, clinical approaches and risk factors. Journal of Small Animal Practice, 2021 (VetCompass study).
- Eiermann J, Schlachet A, Schuller S, Lutz B. Hypoadrenocorticism in dogs presenting to a tertiary veterinary clinic in Switzerland. Schweizer Archiv für Tierheilkunde, 2025.
- Bovens C, Tennant K, Reeve J, Murphy K. Basal serum cortisol concentration as a screening test for hypoadrenocorticism in dogs. Journal of Veterinary Internal Medicine, 2014.
- Da Silva AJ, Gunn E, Guzmán Ramos PJ, Shiel RE, Bree L, Mooney CT. Comparison between typical primary and eunatraemic, eukalaemic hypoadrenocorticism: 92 cases. Irish Veterinary Journal, 2024.
- Mazzaferro E. Hypoadrenocorticism: insidious and deadly. LAVC Annual Conference, 2018. Conference proceedings hosted by IVIS.
- McKean KA, Fellman C. Desoxycorticosterone pivalate for dogs with Addison's disease. Today's Veterinary Practice, 2021.
- Bruyette D. Disorders of the adrenal glands in dogs. Merck Veterinary Manual (pet owner version), May 2026.
- Kintzer PP, Peterson ME. Treatment and long-term follow-up of 205 dogs with hypoadrenocorticism. Journal of Veterinary Internal Medicine, 1997.
About this article
Last updated : fully rewritten using a VetCompass study of 905,543 dogs, the Merck Veterinary Manual, the 2025 ALIVE endocrine consensus, published diagnostic and treatment studies, the University of Illinois, VCA and IVIS-hosted proceedings; added the research summary, signs, adrenal crisis, risk factors, atypical Addison's, diagnosis, treatment, outlook, key takeaways and FAQ.
This page is for general information and is not a substitute for an exam by your veterinarian.
