Addison’s Disease in Dogs: Signs, Causes & Treatment

Addison’s disease (hypoadrenocorticism) is a hormonal disorder in which the adrenal glands produce too little cortisol and aldosterone. Known as “the great pretender” for its vague symptoms, this guide covers causes, signs, diagnosis, and lifelong treatment.

This guide is for informational purposes and is not a substitute for veterinary diagnosis or treatment. Seek immediate veterinary care if your dog collapses or shows signs of a crisis.

What Is Addison’s Disease?

Addison’s disease, or hypoadrenocorticism, is the opposite of Cushing’s disease — instead of producing too much cortisol, the adrenal glands produce too little of the hormones the body needs, primarily cortisol and aldosterone. Aldosterone regulates sodium, potassium, and fluid balance, so a deficiency can cause serious electrolyte imbalances that affect heart function and overall stability.

Addison’s disease is sometimes called “the great pretender” because its symptoms are vague and intermittent, closely mimicking many other conditions, which makes it a challenging diagnosis. It most commonly affects young to middle-aged female dogs, though males and dogs of any age can be affected, and certain breeds — including Standard Poodles, Portuguese Water Dogs, Bearded Collies, and Nova Scotia Duck Tolling Retrievers — have a higher genetic predisposition.

The disease is far less common than Cushing’s disease but can be life-threatening if not recognized and treated, particularly during an “Addisonian crisis,” a sudden and severe collapse requiring emergency care.

Causes & Risk Factors

The most common cause of Addison’s disease is immune-mediated destruction of the adrenal cortex, where the dog’s own immune system mistakenly attacks and damages adrenal tissue over time. This gradual destruction means clinical signs often don’t appear until 85–90% of adrenal function is lost.

Less commonly, Addison’s disease can result from damage to the pituitary gland (which signals the adrenals to produce hormones), certain medications, or abrupt discontinuation of long-term steroid treatment, since the adrenal glands can become suppressed and slow to resume normal function after prolonged steroid use.

Genetics appear to play a meaningful role given the breed predispositions observed, and research continues into specific genetic markers that could allow earlier screening in at-risk breeds.

Signs & Symptoms

Addison’s disease symptoms are often vague, intermittent, and easy to dismiss early on — lethargy, reduced appetite, occasional vomiting or diarrhea, and weakness that seems to come and go, sometimes improving temporarily with fluids or rest before recurring. This waxing-and-waning pattern is a hallmark of the disease and a key clue for veterinarians.

As the disease progresses or during periods of physical or emotional stress, dogs can experience a sudden, severe crisis called an Addisonian crisis, marked by collapse, severe weakness, vomiting, diarrhea, dehydration, and dangerously abnormal heart rhythm caused by high potassium levels. This is a true medical emergency requiring immediate veterinary treatment.

Because symptoms overlap so heavily with gastrointestinal illness, kidney disease, and other conditions, many dogs go through multiple vet visits before Addison’s is correctly diagnosed — a pattern worth being aware of if your dog has recurring, unexplained bouts of lethargy and GI upset.

Diagnosis & Treatment

Diagnosis relies on blood work showing characteristic electrolyte imbalances (low sodium, high potassium) along with an ACTH stimulation test, which is considered the definitive test for confirming Addison’s disease by measuring how the adrenal glands respond to stimulation. Additional blood work rules out other causes of similar symptoms.

Treatment involves lifelong hormone replacement therapy — typically a mineralocorticoid medication (such as DOCP injections given every 3–4 weeks) to replace aldosterone, plus a glucocorticoid (such as low-dose prednisone) to replace cortisol, especially during times of stress, illness, or travel. Regular blood work is used to fine-tune dosing over time.

Dogs experiencing an Addisonian crisis require emergency hospitalization with IV fluids, electrolyte correction, and injectable steroids to stabilize them before transitioning to long-term oral or injectable maintenance therapy.

Managing Addison’s Disease Long-Term

With consistent treatment, dogs with Addison’s disease typically go on to live a normal lifespan and good quality of life. The key to long-term success is strict adherence to the medication schedule and regular veterinary monitoring, since both under- and over-treatment can cause problems.

Owners should keep a small emergency kit of injectable steroid (as prescribed by their vet) on hand for stressful situations like boarding, travel, or illness, and should never abruptly stop medication without veterinary guidance. It’s also worth discussing a stress-dose protocol with your vet for planned stressful events such as grooming, boarding, or travel.

Because Addison’s disease can be triggered or worsened by stress, maintaining a calm, consistent routine and promptly contacting your veterinarian at the first sign of lethargy, vomiting, or appetite changes helps catch potential flare-ups before they become an emergency.

Frequently Asked Questions

Suspect your dog may have Addison’s disease? Don’t wait out vague symptoms — find a veterinarian through HeiBob’s veterinary directory for prompt testing and diagnosis.