A little clarity. A lot of love.
AI DiagAnimalsMADE FOR THE ONES YOU LOVE
English

Language and region

Understand their results
Menu
DISEASE · DOGS

Addison’s disease in dogs: the blood work clues and the ACTH test

Addison’s disease (hypoadrenocorticism) means the adrenal glands do not make enough cortisol, and often not enough aldosterone either. Its signs are vague and come and go, which is why it is called “the great pretender”. Routine blood work often holds the clues that lead vets to the right test.

Written by the AI DiagAnimals editorial teamReviewed by the AI DiagAnimals TeamUpdated Our editorial policy

The essentials

Addison’s disease is a lack of adrenal hormones, usually from autoimmune damage. Signs are vague: tiredness, poor appetite, vomiting, diarrhoea, weight loss, sometimes collapse. Blood work clues include a sodium:potassium ratio below 27, a high potassium and the absence of a stress leukogram in a sick dog. Up to 25–30% of dogs have normal electrolytes. Only the ACTH stimulation test confirms the diagnosis.

Have your dog’s results in front of you? Get every value explained in plain language. Upload the report

What Addison’s disease is

The adrenal glands make cortisol, which helps the body handle stress, and aldosterone, which balances sodium and potassium. In Addison’s disease, the adrenal cortex is damaged, usually by the immune system; it can also follow the sudden withdrawal of steroid medicines [1].

Most affected dogs are young to middle-aged, and Standard Poodles, Portuguese Water Dogs and Great Danes are among the breeds at higher risk [1].

Symptoms of Addison’s disease in dogs

  • Tiredness, weakness and poor appetite, often waxing and waning.
  • Vomiting, diarrhoea and weight loss.
  • Shaking, collapse or a very slow heartbeat in a crisis.

Dogs without electrolyte changes (“atypical” Addison’s) more often have a chronic course with vomiting, lethargy, poor appetite and diarrhoea [1]. Chronic digestive signs are one reason vets check cortisol: see our ACTH stimulation test article.

The blood work clues

None of these findings proves Addison’s disease; together, they lead to the ACTH stimulation test.
FindingWhat it suggestsRead more
Sodium:potassium ratio below 27Lack of aldosterone; suggestive but not specific [1, 2].Potassium
High potassium, low sodiumThe classic electrolyte pattern; normal in up to 25–30% of dogs [1].Potassium
No stress leukogram in a sick dogNormal or high lymphocytes and eosinophils where cortisol would lower them; a low lymphocyte count makes Addison’s very unlikely [1, 3].White blood cell count
High BUN and creatinineDehydration and poor kidney blood flow; in one study, 3 of 34 dogs with apparent acute kidney injury had Addison’s disease [4].BUN in dogs
Low albumin, cholesterol or glucoseCommon, especially in atypical Addison’s [1, 5].Albumin
High calciumSeen in about a third of dogs in one UK study [6].High calcium

How it is confirmed

  • Resting cortisol: above 2 µg/dL, Addison’s is ruled out with near certainty, unless the dog has received a steroid that interferes with the test. Below 2 µg/dL does not diagnose it: most of these dogs do not have the disease [1].
  • ACTH stimulation test: the only definitive test. A cortisol that stays below about 2 µg/dL one hour after synthetic ACTH confirms the disease [1].
  • Atypical Addison’s: in a study of 29 dogs with normal electrolytes, 96.6% had a lymphocyte count above 1,750/µL, and a low albumin-to-globulin ratio was common. No single result could rule the disease out without a cortisol test [5].

Steroid medicines, including creams and drops, can suppress cortisol and mimic the disease: tell your vet about every product your dog receives [1].

How to read the ACTH stimulation result

Here is an example of a post-ACTH cortisol line, followed by a converter for reports in nmol/L.

An annotated line from a lab report · Illustrative example
AbbreviationResultUnitLaboratory intervalFlag
Cortisol post Cortisol 1 hour after ACTH0.6µg/dL> 2L
  1. Abbreviation The second cortisol of the ACTH stimulation test, taken about one hour after the injection.
  2. Result 0.6 µg/dL in this illustrative line: the adrenal glands did not respond.
  3. Unit µg/dL in the United States, nmol/L in Europe: 0.6 µg/dL ≈ 17 nmol/L.
  4. Laboratory interval A post-ACTH cortisol below about 2 µg/dL, or below the laboratory cut-off, confirms Addison’s disease [1].
  5. Flag Very low after stimulation: the pattern of Addison’s disease, provided no interfering steroid was given [1].

Unit converter

Equivalent values

  • Cortisol, nmol/L–

Conversion only changes the unit. Compare the result with the interval printed by the laboratory that measured it.

The Addisonian crisis

An Addisonian crisis is a state of shock with a severely high potassium and low sodium. It is an emergency treated with intravenous fluids and correction of the potassium, blood sugar and acidity [1]. A high potassium can disturb the heart rhythm [2]. The crisis can look like sudden kidney failure, with high kidney values that improve once Addison’s is treated [4].

Related articles

ACTH stimulation test

How the test works and how its two results are read.

Read the article

Cushing’s disease in dogs

The opposite problem: too much cortisol.

Read the article

En français : la maladie d’Addison chez le chien.

Questions to ask your veterinarian

  1. Do my dog’s electrolytes and white cells fit with Addison’s disease?
  2. Should we measure a resting cortisol or go straight to an ACTH stimulation test?
  3. Has my dog received any steroid that could affect the result?
  4. Is it a typical or an atypical form?
  5. How will treatment be monitored, and what should I do in a stressful situation?
YOUR PET’S FULL REPORT

Get your dog’s electrolytes and cortisol tests explained.

AI DiagAnimals reads sodium, potassium, the white cells, the kidney values and the cortisol tests together with your laboratory’s intervals, and prepares the questions for your vet. The service opens soon: leave your email to be told first.

Explain my dog’s reportSee a sample report

Frequently asked questions

What are the first signs of Addison’s disease in dogs?

Vague signs that come and go: tiredness, poor appetite, vomiting, diarrhoea and weight loss. Some dogs are first seen in a crisis with collapse [1].

Can a dog have Addison’s disease with normal electrolytes?

Yes. Up to 25–30% of dogs have normal sodium and potassium; this is called atypical Addison’s disease [1].

Which dog breeds get Addison’s disease?

Any dog can, but Standard Poodles, Portuguese Water Dogs and Great Danes are among the breeds at higher risk [1].

What is the life expectancy of a dog with Addison’s disease?

Once diagnosed and treated, many dogs live a normal life, with regular check-ups of the electrolytes.

How is Addison’s disease monitored in dogs?

With regular clinical checks and blood tests, mainly sodium and potassium, at intervals set by your vet [1].

Sources

  1. Bugbee A et al. 2023 AAHA Selected Endocrinopathies of Dogs and Cats Guidelines. J Am Anim Hosp Assoc. 2023;59(3):113-135. doi.org/10.5326/JAAHA-MS-7368
  2. eClinPath, Cornell University College of Veterinary Medicine. Potassium. eclinpath.com/chemistry/electrolytes/potassium
  3. eClinPath, Cornell University College of Veterinary Medicine. Leukogram patterns. eclinpath.com/hematology/leukogram-changes/leukogram-patterns
  4. Roșca Ș et al. Addisonian crisis mimicking acute kidney injury in dogs: a retrospective study of 34 dogs diagnosed with acute kidney injury in Romania. Life (Basel). 2026;16(1):127. doi.org/10.3390/life16010127
  5. Reagan KL et al. Characterization of clinicopathologic and abdominal ultrasound findings in dogs with glucocorticoid deficient hypoadrenocorticism. J Vet Intern Med. 2022;36(6):1947-1957. doi.org/10.1111/jvim.16564
  6. Hall H et al. Prevalence of hypercalcemia in primary hypoadrenocorticism in dogs: multicenter, retrospective study. J Vet Intern Med. 2023;37(5):1685-1693. doi.org/10.1111/jvim.16786

Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.

Cookie Policy