Addison’s disease is a failure of the adrenal glands to produce enough of the hormones that regulate stress, salt and water balance. Its signature is a dog who is repeatedly unwell with vague signs, appears to recover, then relapses weeks later. It is uncommon, easily missed, and can escalate into a life-threatening crisis.
Why it earned the nickname
Veterinary medicine calls this one the great pretender, and the name is well deserved. There is no single dramatic sign that points at it. Instead there is a dog who has been off their food, a bit flat, maybe vomiting, perhaps with loose stool, who then perks up over a few days and seems fine again. The relapsing pattern is the clue, and it is also the reason it gets missed. Each individual episode looks like a mild stomach upset, and each apparent recovery is genuine, so nobody connects the third episode to the first. Owners often feel faintly silly bringing in a dog who has already improved by the time of the appointment. Please bring them in anyway. That history is the diagnosis. If you have a dog who has been unwell three or four times this year with nothing ever quite adding up, say exactly that, and say it as a pattern rather than describing only the latest episode.
What the adrenal glands do
Two small glands sit near the kidneys and produce hormones that matter enormously. One group regulates the body’s response to stress and helps maintain blood sugar and blood pressure. Another controls the balance of sodium and potassium, and through that, hydration and blood volume. In Addison’s disease, most commonly, the immune system gradually destroys the tissue that produces these hormones. As the reserve shrinks, the dog copes with ordinary days but cannot mount a response when something demands one. A stressful event, a boarding stay, a house move, a long journey or an illness, is often what tips a compensating dog into an obvious episode. There is also a form caused by abruptly stopping long-term steroid treatment. That is worth knowing because it is preventable: never stop a steroid treatment suddenly, and always taper under veterinary direction.
The signs, and who tends to be affected
- Repeated episodes of vomiting or diarrhoea that resolve and return
- Lethargy, or a dog who is intermittently “just not right”
- Poor or variable appetite, and gradual weight loss
- Weakness, shaking, or reluctance to exercise
- Drinking and urinating more than usual
- Episodes that follow a stressful event by a day or two
- A slow heart rate, which is unusual for a dog who is unwell and is a genuine clue
- Collapse, in the acute form
It is most often diagnosed in young to middle-aged dogs, more commonly in females, which sets it apart from many conditions people associate with old age. Recognised predispositions include Standard Poodles, Portuguese Water Dogs, Bearded Collies, West Highland White Terriers, Great Danes and Nova Scotia Duck Tolling Retrievers, although any dog can be affected. It is rare in cats. Because so many of these signs point elsewhere first, the wider picture of what warrants investigation is worth reading in our guide to recognising change in an aging pet, and increased drinking specifically is covered in our post on urinary problems in Mission pets.
An Addisonian crisis is an emergency
This is the presentation nobody should miss. When the hormone reserve runs out entirely, potassium rises, sodium falls, blood volume drops and the heart slows dangerously. A dog in crisis is profoundly weak or collapsed, often cold, with pale gums and a heart rate that is slow rather than fast. They may be vomiting, unable to stand, or unresponsive. This needs immediate treatment with intravenous fluids and supportive care, and that is exactly what our urgent care team is set up to deliver. Phone ahead and go. The reassuring part is that dogs in crisis usually respond well to prompt treatment, and many go on to live entirely normal lives once the condition is identified and managed. The danger is in the delay, not in the disease being untreatable.
How it is diagnosed
Routine bloodwork often gives the first hint, typically through the balance of sodium and potassium, along with changes in kidney values and hydration. Those findings raise suspicion but do not confirm anything on their own, and importantly, a dog between episodes can have bloodwork that looks entirely unremarkable. That is another reason the history matters so much. Confirmation requires a specific test that measures how the adrenal glands respond to a stimulating hormone, with blood samples taken before and after. It is straightforward but it takes part of a day, which is why the appointment is longer than a routine visit. Our diagnostic services carry out that testing, and the results are read in a medical consultation together with everything you have described. There is also a less common form in which the salt-balancing hormone is still normal and only the stress hormone is deficient. Those dogs do not show the classic electrolyte changes at all, which makes them harder still to catch, and they are often the ones investigated for months for chronic gastrointestinal disease.
Living with it
This is genuinely one of the better outcomes in chronic veterinary medicine. Addison’s disease is not curable, but it is very manageable, and a treated dog typically has a normal life expectancy and normal quality of life. Treatment replaces the missing hormones, selected and monitored by your veterinarian, with periodic bloodwork to adjust the dose. That monitoring is not optional and it is not a formality, particularly in the first year while the right dose is established. The practical part for owners is anticipating stress. Because an affected dog cannot mount its own stress response, planned stressful events, boarding, surgery, travel, a house move, are discussed with your veterinary team in advance so the plan can be adjusted around them. Tell any veterinary professional treating your dog that they are Addisonian, including out of hours and at any other practice. Do not skip doses and do not stop treatment because your dog seems well. Seeming well is the treatment working. Ongoing monitoring belongs in a wellness exam schedule, and our post on veterinary diagnostics in Mission explains what that testing involves.
Frequently asked questions
What are the early signs of Addison’s disease in dogs?
Vague and intermittent ones: episodes of vomiting or diarrhoea that resolve and return, lethargy, a variable appetite, weight loss, weakness and increased drinking. The pattern of repeated illness with genuine recovery in between is more informative than any single sign, and episodes often follow a stressful event by a day or two.
Why did my vet not find it the first time?
Because between episodes an affected dog can have entirely unremarkable bloodwork, and each individual episode looks like a routine stomach upset. It is genuinely difficult to spot early and it is not a failure of care. What changes the picture is the pattern over time, which is why describing the whole history rather than only the current episode is so valuable.
Is Addison’s disease fatal?
An untreated Addisonian crisis is life threatening and needs emergency treatment. Once identified and managed, however, the outlook is genuinely good: most treated dogs have a normal life expectancy and a normal quality of life. The risk lies in the condition going unrecognised, not in it being untreatable.
Which dogs are most at risk?
It is most often diagnosed in young to middle-aged dogs and more commonly in females, which surprises owners who associate hormonal disease with old age. Standard Poodles, Portuguese Water Dogs, Bearded Collies, West Highland White Terriers, Great Danes and Nova Scotia Duck Tolling Retrievers are among the recognised predisposed breeds, though any dog can develop it. It is rare in cats.
Can stopping steroid treatment cause it?
Yes. Abruptly stopping long-term steroid treatment can produce a similar crisis, which is why a steroid treatment should never be discontinued suddenly and should always be tapered under veterinary direction. If you are unsure how to reduce a treatment your pet is on, ask before changing anything.
Will my dog need treatment forever?
Yes, because the hormones the body can no longer produce have to be replaced. That is very manageable in practice, with periodic bloodwork to keep the dose right, especially during the first year. Never skip doses or stop because your dog seems well, and let your veterinary team know in advance about planned stressful events such as boarding or surgery.