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Neutering and spaying: When is the right age for a dog?

Dr. Jerry Klein, American Kennel Club on

Published in Cats & Dogs News

In the United States, it is now common to have all dogs and cats not meant for breeding purposes spayed (ovariohysterectomy) or neutered (castration). In fact, 78% of dog-owning households have spayed or neutered their canine companions, according to the American Pet Products Association’s 2019-2020 National Pet Owners survey.

This near-routine practice was a result of veterinarians and the animal shelter community working together to reduce the number of unwanted animals that would be euthanized. Currently, Statista estimates that 6.5 million animals enter U.S. animal shelters each year. Of that number, it’s estimated that 1.5 million are euthanized. Although the euthanasia has decreased over the last decade or so, there remains a very strong case for routine spay/neuter of pet cats and dogs.


Often, the spay and neuter takes place at a very young age for pets, often at 4-6 months. However, studies have shown this may not be the best age to spay or neuter your dog. The relationship between sex hormones and canine health was not well considered and understood decades ago when the early spay/neuter campaigns were started. Today, we are discovering that possibly some of those decisions may have affected the health of some dogs.

Research conducted by the University of California, Davis, reveals that for some dog breeds, neutering and spaying may be associated with the increased risks of certain health conditions such as joint disorders including hip or elbow dysplasia, cranial cruciate rupture or tear and some cancers, such as lymphoma, mast cell tumor, hemangiosarcoma and osteosarcoma. The research conclusions are not surprising. Sex hormones are important in the development of any animal. We know they affect psychological development as well as the musculoskeletal, cardiovascular and the immune system.

Interestingly though, different breeds and different sized dogs mature at different ages, which means early spay/neuter may not be bad for all dogs. The wide margin of maturation of dogs varies considerably, as toy breed dogs mature sexually as early as 6-9 months of age whereas large and giant breeds may mature as late as 16-18 months of age. The end conclusion is that generally, the larger breeds had possibly more to risk in future health conditions in than small or toy breeds of dogs due to early spaying or neutering since they mature at a later age.



The American Veterinary Medical Association “promotes the professional judgement of the veterinarian in developing an informed, case by case assessment of each individual patient, taking into account all the potential risks and benefits of spay/neuter.”

My opinion on the topic is the best age to spay or neuter should no longer be the standard “6 months of age” response many veterinarians have used as a guideline over the years, but rather tailored to each individual dog especially if the dog is a large or giant breed. If you have a purebred dog, you should also speak with your breeder who may be able to provide valuable insight. Then, a discussion with your veterinarian based on your dog’s breed or breed type, sex and potential future medical concerns must be had.

An age of 6-9 months of age may be appropriate for neutering or spaying a toy breed puppy or small breed puppy but a larger or giant breed may need to wait until they are near or over 12-18 months of age. It is also important to understand that often, the earlier these procedures are done, the easier the surgeries usually are for the veterinarian and recovery for the patient. The one rule I recommend is to not knowingly spay a female dog while they are going through their heat cycle as that may exacerbate excessive bleeding.


Spaying and neutering pets remains an important part of the effort to reduce the number of unwanted animals and unnecessary euthanasia in this country. When considering whether to spay or neuter your dog, with today’s information about the possible effects of age at the time of surgery on their future health, it is ideal to have a detailed discussion with your veterinarian to determine what is best for your dog.

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