Oleander poisoning in dogs and cats
Toxic agent: Oleandrin and other cardiac glycosides · Reviewed 2026-08-18
Phone a vet now, before reading on. Have ready: your pet's weight, roughly how much was eaten and when, and the packaging if there is any. ASPCA Animal Poison Control (+1 888 426 4435), Pet Poison Helpline, or Animal PoisonLine in the UK.
Oleander attacks the heart directly. It works like an overdose of the heart drug digoxin, and a single leaf can be enough — including a dried leaf in garden waste or smoke from burning clippings.
What it actually does
Cardiac glycosides inhibit the sodium-potassium pump in heart muscle. Intracellular calcium rises, contractility increases and the electrical conduction of the heart becomes unstable. Potassium leaks out of cells into the blood, which makes the arrhythmias worse. The result is a heart that beats too slowly, too fast, or chaotically.
How much matters
The whole plant is toxic and remains toxic when dry:
| A single leaf | reported as potentially lethal to a dog or cat |
|---|---|
| Dried clippings | just as toxic as fresh — a common exposure in garden waste |
| Smoke from burning it | toxic to inhale |
| Water from a vase | toxic |
| Skewers and sticks | using oleander branches for cooking has poisoned people and animals |
High blood potassium is a defining feature and it is what kills. That makes this a case where a vet wants bloods and an ECG immediately, not observation at home.
What you will see, and when
Onset: 30 minutes to a few hours. Typical course: 24 to 72 hours of cardiac monitoring.
- 30 min – 2 hoursDrooling, vomiting, abdominal pain, diarrhoea
- 2–6 hoursSlow or irregular heartbeat, weakness, cold extremities, collapse
- 6+ hoursLife-threatening arrhythmias, high blood potassium, cardiac arrest
What the vet will do
Decontamination and activated charcoal, continuous ECG, treatment of high potassium, atropine for a dangerously slow heart, and antiarrhythmics. Digoxin-specific antibody fragments — the human digoxin antidote — can be used and are effective, though cost and availability limit them.
Outlook
Guarded. Better with early presentation and cardiac monitoring; sudden death does occur.
Dogs and cats are not the same here
Both, plus horses and livestock. Cats are less likely to chew it but are equally susceptible.
Where it comes from in a normal house
- Hedges and ornamental shrubs in warm climates
- Patio pots and conservatory plants
- Garden waste piles and bonfires
- Dried flower arrangements
The thing people get wrong
“The plant has been cut down, so the danger is gone.”
Drying does not destroy cardiac glycosides. Clippings in a pile, dried leaves on a lawn and smoke from a bonfire are all documented exposures — cutting it down creates the hazard rather than removing it.
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Get PawLife on the App StoreFrequently asked questions
How much Oleander is dangerous?
High blood potassium is a defining feature and it is what kills. That makes this a case where a vet wants bloods and an ECG immediately, not observation at home.
How long after exposure to Oleander do symptoms start?
30 minutes to a few hours. Drooling, vomiting, abdominal pain, diarrhoea. 24 to 72 hours of cardiac monitoring.
Is Oleander worse for cats or dogs?
Both, plus horses and livestock. Cats are less likely to chew it but are equally susceptible.
Is it true that: The plant has been cut down, so the danger is gone.
Drying does not destroy cardiac glycosides. Clippings in a pile, dried leaves on a lawn and smoke from a bonfire are all documented exposures — cutting it down creates the hazard rather than removing it.
Related emergencies
Sources
This page is information, not veterinary advice. Toxic doses vary with body weight, age, breed and individual sensitivity, and the figures above exist to explain what a vet is assessing, never to decide that an amount is safe. If you are reading this because something has already been eaten, call a vet.