Are Hydrangeas Poisonous to Cats?

Barri J. Morrison, DVM
By Barri J. Morrison, DVM on Oct. 30, 2023
A cat sits among hydrangea plants.

What Is Hydrangea Poisoning in Cats?

Hydrangea shrubs, known for their stunning and colorful flowers, are commonly found in gardens and as houseplants. They are also frequently used as floral decorations for special events. These plants have broad, flat green leaves and large flower clusters that come in various colors, including pink, red, blue, purple, and white. These flowers are popular due to their large clusters that resemble balls of snow.

The hydrangea is also called the hortensia plant, hills of the snow, or seven bark, and shares the same toxin found in almonds, apple and pear seeds, and pits from fruits in the prunus species (cherry, peach, apricot, and plum).

All parts of the hydrangea plant are toxic, but the highest concentration is found in the leaves and flowers.

While severe toxicity is very rare, mild poisoning is common and often leads to stomach upset in cats when they consume large amounts. The toxic substance in hydrangeas is called amygdalin, a cyanogenic glycoside that is also toxic in dogs, horses, and livestock.

This toxin is activated when the plant is chewed, and it can trigger cyanide poisoning. Cyanide is a fast-acting toxin that enters the bloodstream and impairs the body’s ability to use oxygen properly.

If you suspect your cat has ingested any amount of a hydrangea plant, they should be seen by their veterinarian as soon as possible or be taken to a veterinary emergency room.

Key Takeaways

  • All parts of a hydrangea plant are toxic to cats, though the leaves and flowers have the highest toxicity.
  • Unfortunately, it’s not known exactly how much hydrangea your cat would need to eat to cause severe toxicity.
  • Don't induce vomiting at home in your pet if they have ingested hydrangea.

How Many Hydrangeas Are Toxic to a Cat?

Unfortunately, it’s not known exactly how much of the hydrangea shrub or flowers your cat would need to eat to cause severe toxicity.

Due to this unknown and the fast-acting toxicity that could occur after any ingestion, pet parents should bring their cat to the vet to ensure that they do not develop cyanide poisoning.

Due to the bright colors of flowers that cats might be attracted to, ingestion can occur quite quickly in a home garden, with a houseplant, or if you take your cat to an event where these flowers are used as decoration.

Cats are more susceptible to hydrangea toxicity than dogs because of their small body size.

Cyanide toxicity from the hydrangea plant is dose-dependent, meaning the more they eat, the higher the chance of developing clinical signs of poisoning.

Symptoms of Hydrangea Poisoning in Cats

Symptoms of hydrangea poisoning in cats include:

In cases of cyanide poisoning, signs made include:

What Should I Do If My Cat Has Eaten a Hydrangea?

If you notice any of these symptoms or suspect your cat has ingested any part of the hydrangea plant, they should see a veterinarian as soon as possible.

It’s always a good idea to bring part of the plant to the vet’s office with you so they can ensure proper identification, which will aid your veterinarian in treating your cat’s symptoms.

If your cat doesn’t have any symptoms, you can call the Pet Poison Helpline (855-764-7661) for advice, but often with this type of toxicity, they will recommend a visit to the vet as well.

If your cat has ingested a substantial amount of hydrangea, time is of the essence, as toxicity will continue to worsen with time and the continued absorption of the toxin.

Do not induce vomiting at home for any possible poison ingestion without explicit direction from your vet to do so.

Since severe hydrangea toxicity is rare, the risks of inducing vomiting are often more severe than the mild toxicity your cat might develop.

Your vet will perform a physical exam and check baseline blood and urine tests to ensure there are no other health concerns. They might even suggest an X-ray of your cat’s abdomen to rule out other causes of digestive upset.

Do not induce vomiting at home for any possible poison ingestion without explicit direction from your vet to do so.

Treatment of Hydrangea Poisoning in Cats

Treatment for hydrangea toxicity in cats involves managing the symptoms, as there is no specific antidote.

The approach to treatment depends on the severity of clinical signs and the amount of hydrangea ingested.

For recent ingestions with cats exhibiting clinical signs but otherwise in good health, your veterinarian might induce vomiting to remove the source of poisoning and prevent further toxin from getting absorbed into the bloodstream.

In severe cases, gastric lavage (stomach pumping) may be performed to physically eliminate plant material from the stomach.

If your cat simply has stomach upset, your vet will likely prescribe antibiotics and anti-nausea medications to help with diarrhea and vomiting.

Dehydration will be treated with fluid administration, either subcutaneously (under the skin) for mild cases or intravenously (IV) for more severe cases.

In severe instances, your cat may need to be hospitalized for supportive care, including oxygen therapy if they have difficulty breathing.

If your cat has an elevated heart rate, an EKG monitor may be used to ensure that their heart rhythm is normal, and medications can be given to help stabilize their heart rate. 

Prognosis of Hydrangea Poisoning in Cats

Cats who show severe clinical signs of poisoning but are still alive two hours or more after the signs begin generally have a good chance of recovery unless cyanide absorption by the digestive system persists. 

In mild cases, once vomiting and diarrhea have stopped and the toxin has been successfully removed from your cat’s digestive system, the prognosis for a full recovery is excellent.

Your cat’s appetite and mood should also improve quickly following the successful removal of the toxin.

Prevention of Hydrangea Poisoning in Cats

While these beautiful and colorful flowers might be tempting to have in your home or garden, it’s best to put them where your cat cannot reach, particularly locations where a cat cannot climb. 

If your cat spends time outdoors, make sure your own garden does not contain toxic plants. And rather than letting your cat roam free, consider options like building a catio or training your cat to walk on a leash with a harness outdoors.

Featured Image: Nils Jacobi/iStock / Getty Images Plus via Getty Images

Barri J. Morrison, DVM


Barri J. Morrison, DVM


Barri Morrison was born and raised and currently resides in Ft. Lauderdale, Florida. She went to University of Florida for her...

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