Suspect poisoning? US: ASPCA Poison Control (888) 426-4435 · UK: 01202 509 000 · Severe symptoms → nearest emergency vet now.

My cat chewed an oleander leaf and now has diarrhea — is this just a stomach upset or poisoning?

Cats · Emergency guide

Last reviewed: 2026-09-05 · Reference ranges: ASPCA, Pet Poison Helpline & Merck Veterinary Manual

Short answer

This is poisoning, not a simple stomach upset. Oleander contains cardiac toxins that can cause fatal heart rhythm disturbances, and diarrhea is often one of the first signs. Other symptoms like weakness, drooling, or an irregular heartbeat can follow within hours. This is an emergency — contact your vet or the ASPCA Animal Poison Control Center at 888-426-4435 immediately, as this toxin can be deadly without prompt treatment.

Why is this dangerous?

Oleander contains oleandrin and other cardiac glycosides — the same class of compound as foxglove and digoxin. They disrupt the sodium-potassium pump in heart muscle and can cause fatal rhythm disturbances.

Dried leaves stay toxic for a long time, and a pet that drinks from a vase of oleander can be poisoned without eating any leaf at all.

Why speed matters

Delaying care significantly worsens outcomes. Some signs appear hours or days later, so "looks fine right now" is not a reason to wait.

Signs to watch for

  • Vomiting, drooling, abdominal pain, diarrhoea
  • Slow or irregular heartbeat, weak pulse
  • Weakness, wobbliness, fainting
  • Pale or bluish gums, cold limbs
  • Seizures and sudden collapse in severe cases

What to do right now

  1. Go to an emergency vet immediately — cardiac glycoside poisoning needs monitoring and can kill within hours.
  2. Do not wait for symptoms. Tell the vet the plant name and how much was eaten or drunk.
  3. Do not induce vomiting unless instructed.
  4. Remove oleander from any garden or yard a pet has access to, and never leave cuttings within reach.
If your pet shows any of the signs above, go to the nearest emergency vet now and call ahead.

The step-by-step response, from the first minute to the vet visit, is in our Oleander emergency guide.

Open the full emergency guide: Oleander →