Hormone Replacement Poisoning in Cats


PetMD Editorial

Updated Aug. 24, 2022

Toxicosis with Hormone Replacement Medidogions in Cats

Hormone replacement therapy (HRT) is used in various forms by many women, including creams, gels, sprays and patches. However, accidental exposure of cats to these hormone replacement products can cause serious illness. Cats are easily poisoned by these products.

Hormone replacement products can also be poisoning to dogs. If you would like to learn how they affect dogs, please visit this page in the petMD health library.

Symptoms and Types

Symptoms associated with hormone replacement poisoning will vary depending on the sex of the cat.

  • Female Cats – Signs similar to being in heat, including a swollen vulva and bloody discharge will be present in female cats experiencing HRT toxicity, even if spayed.
  • Male Cats – Extreme attraction to female dogs as well as the possibility of swollen mammary glands (breasts) and abnormally small penis. In unaltered cats, testicular atrophy (shrinking of the testicles) may also occur.
  • Hair loss may occur in both male and female cats.

There is also concern that prolonged exposure to HRT products could cause bone marrow suppression leading to aplastic anemia (a severe blood disease) and possibly mammary tumors (breast cancer.)


Hormone replacement therapies are used in women to replace estrogen and treat symptoms of menopause such as hot flashes, mood swings and bone loss. HRT medications are commonly supplied as creams, gels, sprays or patches. Women are often advised to apply the medication to the wrists, inner elbows, or legs.

Cats typically become exposed by licking the HRT medication from a woman’s skin. They may also be exposed by chewing on or licking discarded patches.


Diagnosis relies on the appearance of expected clinical signs and known (or suspected) exposure to an HRT product. Estrogen levels can also be measured in the blood to confirm the diagnosis, if necessary.


Symptoms are often reversible by eliminating further exposure to the medication. However, symptoms may take months to resolve completely in some cases.


  • Women should apply hormone replacement therapy products to areas of the body that the cat is not likely to contact.
  • When applying HRT products, women should wear gloves. The gloves should be disposed of in a location inaccessible to the cat when finished.
  • Used patches and similar items should be discarded out of the cat’s reach.

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