Side Effects of Dog Neutering

The decision to neuter should be made on an individual basis.
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Dog owners are frequently encouraged to neuter their dogs, typically at 6 months of age. However, recent research calls into question that one-size-fits-all approach. Various factors including breed, genetics, environment, health history and lifestyle affect the decision of whether to neuter, and at what age.

Surgical Effects

Neutering is generally considered a "routine" surgery, but it does carry the typical surgical risks. Some breeds, and some families within breeds, are sensitive to surgical and post-surgical drugs, and some pre-existing conditions can increase the risk of complications. Always discuss surgery risks with your vet to see whether special precautions are needed; also check with your breeder to see whether there's a family history of problems with surgery.

Long-Term Health Effects

In the past, surgical complications were considered the only risks of neutering. But recent research has identified a growing number of potential long-term health risks associated with the surgery. In studies, neutered dogs had a higher incidence of hypothyroidism, obesity, orthopedic disorders, cognitive impairment, vaccine reactions and various cancers than did intact dogs. In some cases, other factors also come into play, such as breed or age at the time of the surgery.

Behavioral Effects

Because neutering eliminates circulating testosterone in a dog's system, sex-related behaviors such as marking or roaming are reduced in many neutered dogs. Although neutering often is suggested to reduce aggression, especially toward other dogs, the science is mixed. Some research shows a decrease in aggression, other studies show an increase or no effect. Other unwanted behaviors, such as barking, begging or stealing food, are actually increased in neutered dogs.


Neutering is usually the most convenient option for a dog owner, because it eliminates the chance of unplanned puppies. Because neutering removes a dog's testicles, it also removes the risk of testicular cancer, although only a small percent of intact dogs develop testicular cancer. Neutering also reduces the risks of benign prostate issues and perianal fistulas.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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