Addison’s disease in dogs, also called hypoadrenocorticism, is a condition where the adrenal glands stop producing enough of two critical hormones: cortisol and aldosterone. It most commonly appears in young to middle-aged dogs and can range from subtle, intermittent symptoms to a sudden life-threatening crisis. The good news is that once diagnosed, most dogs with Addison’s disease live normal, full lives with ongoing medication.
What the Adrenal Glands Normally Do
Dogs have two small adrenal glands that sit near the kidneys. The outer layer of each gland, called the cortex, produces two types of hormones that are essential for survival. Cortisol helps the body respond to stress, regulates metabolism, controls blood sugar, and supports the immune system. Aldosterone manages the balance of sodium and potassium in the blood, which directly affects hydration, blood pressure, and heart function.
In Addison’s disease, the adrenal cortex is gradually destroyed, most often by the dog’s own immune system attacking the tissue. As hormone production drops, the body loses its ability to handle even routine stressors like a car ride, a grooming appointment, or a change in routine. Less commonly, Addison’s can develop if a dog has been on long-term steroid medications that are stopped too quickly, causing the adrenal glands to atrophy from disuse.
Breeds and Dogs at Higher Risk
Any breed can develop Addison’s disease, and mixed-breed dogs are actually diagnosed most frequently. However, certain breeds are significantly overrepresented. According to Cornell University’s College of Veterinary Medicine, predisposed breeds include Standard Poodles, West Highland White Terriers, Bearded Collies, Great Danes, Portuguese Water Dogs, Labrador Retrievers, Rottweilers, and Wheaten Terriers. Nova Scotia Duck Tolling Retrievers also carry a notable genetic predisposition. Female dogs are affected more often than males.
The typical age at diagnosis is young to middle adulthood, though cases have been reported across a wide age range. If you own one of these breeds and your dog develops vague, recurring symptoms that your vet can’t pin down, Addison’s is worth bringing up.
Symptoms That Come and Go
Addison’s disease is sometimes called “the great pretender” because its symptoms mimic so many other conditions and often appear intermittently. A dog might seem off for a few days, then bounce back to normal, only to get sick again weeks later. This waxing and waning pattern is one of the disease’s hallmarks and a major reason it gets missed early on.
Common signs include:
- Lethargy and weakness: your dog seems unusually tired, reluctant to walk, or slower than normal
- Loss of appetite and weight loss: gradual or sudden disinterest in food
- Vomiting and diarrhea: gastrointestinal upset that may be intermittent or persistent
- Increased thirst and urination: from the body’s inability to regulate sodium and water balance
- Shaking or trembling: particularly during stressful situations
- Muscle weakness or a wobbly gait
These symptoms often get worse during periods of stress. A dog that was managing fine at home might collapse after boarding, surgery, or even a thunderstorm. Because cortisol is the body’s stress-response hormone, dogs without enough of it simply cannot cope with situations that healthy dogs handle easily.
Addisonian Crisis: The Emergency
If Addison’s disease goes undiagnosed long enough, or if a dog with unrecognized disease encounters a major stressor, the result can be an Addisonian crisis. This is a medical emergency. The dog’s potassium levels spike dangerously high while sodium drops, leading to severe dehydration, a dangerously slow heart rate, low blood pressure, and potentially collapse or shock.
A dog in crisis may appear extremely weak, unresponsive, or limp. Some dogs have a slow, irregular heartbeat that a vet can detect immediately. Without emergency treatment involving aggressive IV fluids and injectable steroids, an Addisonian crisis can be fatal. Many dogs are actually first diagnosed with Addison’s disease during one of these emergencies, because the earlier, milder symptoms were attributed to something else.
Typical vs. Atypical Addison’s
Veterinarians distinguish between two forms of the disease. In typical Addison’s, both cortisol and aldosterone production are deficient. This is the more common and more recognizable form because the loss of aldosterone throws off the sodium-to-potassium ratio in the blood. A normal dog’s sodium-to-potassium ratio is roughly 27:1 to 40:1. In typical Addison’s, this ratio drops below 27:1, and values under 24:1 are strongly suggestive of the disease.
In atypical Addison’s, only cortisol production is affected while aldosterone remains normal or close to it. Because electrolytes look fine on routine bloodwork, atypical cases are harder to catch. These dogs still have all the vague symptoms of lethargy, GI issues, and poor stress tolerance, but the classic electrolyte red flag is missing. Some atypical cases eventually progress to typical Addison’s as more of the adrenal cortex is destroyed.
How Addison’s Disease Is Diagnosed
Routine bloodwork often provides the first clues. Dogs with typical Addison’s will show high potassium and low sodium on a basic chemistry panel. Another subtle hint is the absence of a “stress leukogram,” a specific pattern of white blood cell changes that normally appears on bloodwork when a dog is sick or stressed. A dog that’s clearly unwell but shows a relaxed, unstressed white blood cell pattern is a red flag for Addison’s.
The definitive test is called an ACTH stimulation test. Your vet draws a blood sample to measure your dog’s baseline cortisol, then gives an injection of a synthetic hormone that tells the adrenal glands to produce cortisol. An hour later, a second blood sample is drawn. In a healthy dog, cortisol rises significantly after the injection. In a dog with Addison’s, both the baseline and the post-stimulation cortisol levels remain very low or undetectable, because the adrenal glands simply can’t respond. It’s a straightforward test that takes about an hour and gives a clear answer.
One important note: if your dog has recently been given steroid medications like prednisone, this can suppress the adrenal glands and produce a false result. Your vet needs to know about any recent steroid use before running the test.
Long-Term Treatment
Treating Addison’s disease means replacing the hormones the adrenal glands can no longer make. For dogs with typical Addison’s (deficient in both cortisol and aldosterone), treatment has two parts.
Aldosterone replacement is handled with an injectable medication given roughly every 25 to 30 days. The injection is administered under the skin, either at the vet’s office or at home once you’re comfortable with the process. Dosing is individualized based on follow-up bloodwork that checks sodium and potassium levels. Research published in the Journal of Veterinary Internal Medicine has shown that many dogs do well on lower doses than originally recommended, which can meaningfully reduce the cost of treatment.
Cortisol replacement is typically managed with a daily oral steroid given at a low, physiologic dose. This replaces only what the body should be producing naturally, so the side effects associated with high-dose steroids (excessive thirst, weight gain, panting) are not usually a concern. During times of extra stress, such as travel, illness, or surgery, your vet may advise temporarily increasing the steroid dose to mimic what a healthy dog’s body would do on its own.
Dogs with atypical Addison’s (cortisol-deficient only) may only need the daily oral steroid, though they require periodic monitoring to make sure their aldosterone production hasn’t started declining too.
What Ongoing Monitoring Looks Like
After diagnosis, your dog will need regular blood tests to make sure electrolytes stay in balance and the medication doses are correct. In the first few months, these checks happen frequently, often every two to four weeks. Once your dog is stable on a consistent dose, monitoring typically shifts to every three to six months.
The adjustments are usually minor. If potassium creeps up or sodium dips, the interval between injections gets shortened or the dose adjusted slightly. Most owners settle into a predictable routine within the first few months.
Prognosis and Quality of Life
The prognosis for dogs with well-managed Addison’s disease is excellent. Once the right medication balance is found, most dogs return to completely normal activity levels and behavior. They play, eat, and enjoy life as if nothing is wrong. The disease itself doesn’t shorten a dog’s lifespan in any meaningful way, provided treatment is consistent.
The main ongoing considerations are cost and routine. The injectable medication can be expensive, though lower-dose protocols are helping reduce that burden. You’ll need to keep a regular schedule for injections and blood monitoring, and you’ll want to have a plan for stressful events so you can adjust the oral steroid dose proactively. Many owners keep an emergency supply of injectable steroids at home in case their dog becomes suddenly ill and can’t keep oral medication down. Your vet can walk you through when and how to use it.
Dogs that were chronically underweight or lethargic before diagnosis often make a dramatic turnaround within the first weeks of treatment. For many owners, the diagnosis is actually a relief, because it finally explains months of mysterious, frustrating symptoms.