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Can estradiol be used for dogs?

Estradiol treats urinary incontinence in dogs
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By | Mar. 11, 2025 Medically reviewed by Emma Ryan, DVM
Brown and white dog with a torn up toy: Can estradiol be used for dogs?

Key takeaways

  • Estradiol use is avoided in dogs, but a veterinarian may use it to treat urinary incontinence in a spayed female or for other estrogen-responsive disorders.

  • Estradiol comes in four forms. Doses depend on the type of estradiol being used.

  • The most common side effects of estrogen therapy in dogs are loss of appetite, vomiting, increased thirst, and swollen genitals in female dogs.

  • Do not give estradiol to dogs if the dog is getting other estrogens, drinking or urinating excessively, or has had an allergic reaction to estradiol doses.

In this article:

Estradiol is a natural estrogen that produces female secondary sexual characteristics, regulates estrus cycles, prepares the body for pregnancy, and affects organs throughout the body. All mammals and most other animals produce estradiol. 

Although estradiol is prescribed to women, veterinarians rarely use estradiol in animals other than female horses (mares). They consider it unsafe because of the risk of bone marrow suppression and uterus diseases. When dogs need estrogen treatment, estriol is the estrogen of choice. 

RELATED: Save up to 80% on estradiol

What is estradiol used for in dogs?

Veterinarians largely avoid using estradiol in dogs. Estradiol (E2) is a natural hormone in dogs, but it’s the most powerful type of estrogen. It also lasts a long time in a dog’s body and can cause serious uterine diseases and suppress bone marrow. Estradiol-induced bone marrow suppression can be fatal in some cases.

In addition to estradiol, dogs also naturally produce two other types of estrogens: estrone (E1) and estriol (E3). These are less powerful than estradiol and less likely to cause side effects. Estrone is the weakest, so it’s not generally used in veterinary medicine. Estriol is powerful enough to treat estrogen-responsive problems. It’s weak enough that serious problems are less of a concern. For this reason, estriol is the preferred estrogen treatment in veterinary medicine. It’s also the only estrogen FDA-approved for use in dogs.

That doesn’t mean veterinarians can’t use estradiol, but its use is discouraged in favor of safer treatments. The primary use of estrogens in veterinary medicine is to treat urinary incontinence in female dogs that have had their ovaries surgically removed. Veterinarians may also use an estrogen to terminate a pregnancy, but there are safer drugs for that purpose.

Urinary incontinence

Canine urinary incontinence has many possible causes, including behavior problems, infections, and anatomical abnormalities. One common cause is a weak urethra sphincter. Called “primary sphincter mechanism incompetence” or PSMI, a weak bladder sphincter isn’t strong enough to hold back the pressure of urine in the bladder. It mainly affects female dogs after they’ve been spayed, and their estrogen levels drop dramatically. About 1 in 5 spayed bitches eventually become incontinent. The incidence is higher in large dogs.

Loss of estrogen causes several changes in a female dog’s body, including gradual changes to the urethra. These changes make the dog less capable of holding back urine. This doesn’t happen right after a spay. It usually takes two to three years after a spay before the dog shows signs of incontinence, such as house soiling.

As a hormone replacement therapy, estrogens have been used in postmenopausal women to treat urinary incontinence. Estrogens also relieve incontinence in spayed dogs. Estrogen therapy relieves weak sphincter urinary incontinence in about 65% to 83% of dogs. So they work, but the danger of possible serious side effects in estradiol is a problem. 

Among the various types of estrogen, estradiol is the least safe to use as a daily treatment in dogs. If estrogen treatment is appropriate, veterinarians use estriol instead. Veterinarians also use a drug called phenylpropanolamine to treat urinary incontinence.

Is estradiol safe for dogs?

Estradiol is not considered safe for dogs, but veterinarians may, on rare occasions, use it. All estrogen treatment is risky in dogs, but estradiol is more likely to cause bone marrow suppression, blood disorders, and uterine diseases than other estrogens. 

Bone marrow suppression usually reverses after estradiol is stopped, but not always. In rare cases, bone marrow suppression may persist and get worse after estradiol is stopped. A dog could lose the ability to make blood cells (aplastic anemia) and die.

Side effects of estradiol in dogs

The most common side effects of estradiol and other estrogen treatments in dogs are:

  • Appetite loss
  • Vomiting
  • Thirst
  • Anxiety
  • Swollen vulva
  • Low energy
  • Drooling
  • Hair loss

The most serious side effects of estradiol in dogs are:

  • Bone marrow suppression
  • Blood disorders
  • Uterine infection (pyometra)
  • Uterine swelling (endometrial hyperplasia)
  • Mammary tumors

If a dog is on estradiol or any other estrogen treatment, contact a veterinarian if you notice any clinical signs of a possible serious side effect, including:

  • Pale gums
  • Decreased energy
  • Nose bleeds
  • Blood in the stools or urine
  • Unusual bleeding
  • Trouble breathing
  • Decreased appetite
  • Fever
  • Depression
  • Vaginal discharge
  • Excessive thirst
  • Excessive urination

Signs that the dog has a serious problem requiring immediate veterinary care include:

  • Complete loss of appetite
  • Listlessness
  • Marked depression
  • Vomiting
  • Diarrhea

Interactions of estradiol with other pet meds

Estradiol is rarely used in dogs. When it is, there are several possible drug interactions that can reduce its effectiveness or increase the risk of serious side effects. Make sure to tell the veterinarian about all your pet’s medications, including prescription drugs, over-the-counter medications, and supplements, particularly:

Estradiol dosage for dogs

Dogs are rarely given estradiol. All published dosages warn veterinarians to avoid the drug and prescribe safer treatments.

The published dosage for estradiol includes:

  • For pregnancy termination: 44 mcg/kg estradiol cypionate intramuscular injection given once OR 10 mcg/kg subcutaneous injection given once during a specific period post-breeding.

There are no veterinary formulations of estradiol. When veterinarians use estrogens, they usually prescribe estriol, sold as a brand-name tablet called Incurin. They can prescribe tablets formulated for people or use tablets specially prepared by a compounding pharmacy. 

Can dogs overdose on estradiol?

Large estradiol doses can be toxic in dogs. Repeatedly overdosing a dog with estradiol or other estrogens can cause noticeable and serious side effects, including bone marrow suppression, uterine infections, and mammary tumors. 

Symptoms of estrogen toxicity in dogs include hair loss, weakness, incoordination, genital swelling in female dogs, and genital atrophy in male dogs. Call a veterinarian if a dog ingests estradiol by accident or a dog on estrogen starts showing side effects.

Can I give my dog estradiol every day?

Estradiol is not safe to give to a dog every day because of possible severe adverse effects. If a veterinarian prescribes daily estradiol, ask about other treatment options.

How to give your dog estradiol

Estradiol is rarely given to a dog. If estrogen therapy is needed, the veterinarian will most likely prescribe estriol (brand-name Incurin). 

If a veterinarian prescribes estradiol or other estrogen, pet caregivers should expect to give oral doses every day. The veterinarian will have to regularly check the dog and adjust the doses, so keep all appointments. After the initial treatment period, doses will be gradually reduced to a low dose.

  • Give this medication as instructed.
  • Do not give more than prescribed or give it more frequently than prescribed.
  • Estradiol or estriol can be administered with or without food.
  • If giving your dog tablets is difficult, ask a veterinary assistant to demonstrate the proper procedure.
  • If a dose is missed, give it when remembered. Do not give a missed dose if it’s almost time for the next dose. Give the next dose as scheduled.
  • If the medication does not work or symptoms get worse, talk to the veterinarian.

Estradiol alternatives for dogs

Although estradiol can help dogs with weak sphincter urinary incontinence, veterinarians consider it hazardous in dogs. The preferred treatments are estriol or phenylpropanolamine (PPA), a drug that increases urethral muscle tone. PPA successfully and safely resolves weak sphincter urinary incontinence in 74% to 92% of dogs. 

For pregnancy termination, the safest and most effective drug for dogs is prostaglandin F2alpha. Other safe treatment options include:

Summary

Veterinarians consider estradiol unsafe for cats and dogs, though they may sometimes prescribe it. Severe adverse effects are possible. Because there are safer and more effective treatments, caregivers should ask about those other drugs before giving a dog estradiol. Caregivers should also be familiar with the clinical signs of a serious adverse reaction and call a veterinary professional immediately at any sign of a serious problem.