A practical guide to canine hypoadrenocorticism covering vague symptoms, Addisonian crisis, electrolytes, ACTH stimulation testing, replacement medicines and stress plans.

Seek emergency care for possible Addisonian crisis

Collapse, extreme weakness, inability to stand or very slow heart rate
Repeated vomiting or diarrhoea with dehydration
Pale gums, cold extremities, low temperature or altered consciousness
Known Addison’s disease with missed medicine, severe illness, surgery or inability to keep tablets down
Tremors, seizures or signs of low blood glucose

What Addison’s disease is

Canine hypoadrenocorticism occurs when the adrenal cortex cannot produce adequate hormones. Cortisol supports circulation, glucose regulation, gastrointestinal function and the response to stress. Aldosterone helps control sodium, potassium, water balance and blood pressure. Primary disease often affects both systems; secondary disease may mainly reduce cortisol.

Because cortisol influences many organs, the signs are famously nonspecific. A dog may be treated repeatedly for gastroenteritis, stress, dietary indiscretion or kidney disease before the pattern is recognised. Symptoms may wax and wane, and routine examination between episodes can appear normal.

Common signs and the Addisonian crisis

Pattern	Possible signs	Why it can mislead
Intermittent gastrointestinal	Vomiting, diarrhoea, poor appetite, weight loss	May look like food intolerance or infection
Weakness and behaviour	Lethargy, shaking, exercise intolerance, hiding	May be attributed to anxiety or heat
Fluid and circulation	Dehydration, collapse, low blood pressure	May resemble shock from many causes
Laboratory pattern	Low sodium, high potassium, low glucose or lack of a stress white-cell response	Not every dog shows every classic change

An Addisonian crisis is an emergency in which hormone deficiency and fluid/electrolyte disturbance cause severe circulatory compromise. Treatment begins before confirmatory results are complete when the clinical risk is high. Intravenous fluids, glucose or electrolyte management and an appropriate corticosteroid may be used under hospital monitoring.

How veterinarians test for Addison’s disease

Initial tests usually include blood count, biochemistry, electrolytes, glucose and urinalysis. A sodium-to-potassium ratio may raise suspicion but cannot diagnose the disease because gastrointestinal, kidney and other disorders can produce similar changes.

A resting cortisol is a useful rule-out test: when it is comfortably above the laboratory’s threshold, Addison’s is unlikely. A low value is not diagnostic because many ill dogs have low resting cortisol. The ACTH stimulation test measures cortisol before and after synthetic ACTH and is the standard confirmation test for most dogs.

Before testing

List every steroid tablet, injection, inhaler, ear drop and skin cream
Report recent fluid therapy or emergency treatment
Provide previous sodium, potassium and cortisol results

Additional assessment

Blood pressure and ECG when potassium is high
Imaging if another abdominal disease is suspected
Endogenous ACTH or aldosterone-related testing in selected cases

Typical, atypical and secondary Addison’s

“Typical” primary Addison’s commonly produces both glucocorticoid and mineralocorticoid deficiency and may cause low sodium and high potassium. “Atypical” presentations may initially have normal electrolytes while cortisol production is inadequate. Some dogs later develop mineralocorticoid abnormalities, so follow-up electrolytes remain important.

Secondary hypoadrenocorticism can occur when pituitary ACTH stimulation is insufficient or after abrupt withdrawal of prolonged steroid therapy. The electrolyte pattern may differ. The treatment plan depends on which hormone systems are deficient.

Lifelong hormone replacement

Stable dogs with primary disease typically receive glucocorticoid replacement and, when aldosterone is deficient, mineralocorticoid replacement. Mineralocorticoid therapy may be injectable or oral depending on availability, cost and the case. Dose adjustments are based on clinical signs, electrolytes and veterinary monitoring—not on body weight alone forever.

The glucocorticoid dose should be the lowest that controls deficiency without causing excessive thirst, urination, hunger, panting, muscle loss or infection risk. Never stop chronic steroid replacement suddenly unless the treating veterinarian provides a taper or replacement strategy.

Important: An owner should not change mineralocorticoid injection intervals or steroid doses based only on one symptom. Vomiting or weakness may be an Addison’s problem, but it may also be another emergency.

Monitoring that prevents both under- and over-treatment

Schedule electrolyte checks at the intervals advised during stabilisation and dose changes.
Record appetite, stool, vomiting, energy, thirst, urination and body weight.
Watch for steroid excess: marked hunger, panting, muscle weakness, skin infection or increased thirst.
Keep medicine names, doses and last administration dates on the phone.
Review new medicines and supplements for interactions or effects on electrolytes.

Build a written stress-dose and emergency plan

Dogs with Addison’s cannot mount a normal cortisol increase during major stress. The veterinarian may prescribe a temporary glucocorticoid increase for surgery, significant illness, long travel, boarding, intense exercise or other predictable stress. The exact plan is individual; “stress” does not mean every exciting event automatically requires a large dose.

Ask the veterinarian to define mild, moderate and emergency stress for this dog.
Write what to do if a tablet is vomited or the dog refuses food.
Give the boarding team exact medicine times and authorisation for veterinary transport.
Carry enough medicine for delays and store injectable products as directed.
Use an emergency card stating “Addison’s disease—steroid dependent” with clinic numbers.

Dogsvilla practical tip: At every vet visit, say “my dog has Addison’s disease” before treatment begins. This matters when fasting, anaesthesia, fluid therapy or new medicines are being planned.