In the U.S., neutering dogs refers to castrating male dogs by removing their testicles and hence lowering their male hormone levels. The main reason veterinarians recommend neutering male dogs is to prevent them from breeding and to prevent annoying male dog behaviors like urine marking, mounting, aggression/fighting and roaming to find female dogs. But when is it too late to neuter a dog in terms of seeing behavioral benefits?

Unwanted behaviors may or may not improve after neutering male dogs over a year old. A 2021 study found some behaviors, like mounting, were reduced 9 months after castration. But the study found urine marking was NOT reduced after dogs were castrated. (7)

However, there have been multiple other studies over the years that have found neutering does improve urine marking behavior in mature male dogs.(6) But the studies might not have followed dogs long enough or did not control well for factors other than neutering. 

When Is It Too Late to Neuter a Dog?

There is no age at which a male dog is too old to be neutered unless he is so sick that he can’t withstand the anesthesia and surgery. But neutering a dog over the age of 12 months may not improve troublesome male dog behaviors.

But should you neuter your older male dog? If he is healthy and has no behavior issues, there is little motivation to neuter him. Neutering only provides improvement of uncommon health risks and is done mostly for behavioral improvements. Many vets won’t push you to neuter your dog (1 year and up) unless he’s having a specific problem that would be improved by neutering. See the following list…

8 Good Reasons to Neuter an Older Dog

  1. Prevents unwanted breeding with female dogs
  2. Prostate disease–hypertrophy, cancer or infection
  3. Perianal gland tumor
  4. Testicular infection or tumor
  5. Chronic bladder infections
  6. Intolerable behavior problems like urine marking, fighting other dogs and roaming/escaping to seek a female dog in season (although neutering might NOT improve these behaviors).
  7. Perineal hernia
  8. Cryptorchidism (undescended testicle(s) in the abdomen-prone to cancer)

Neutering Older Dogs Side Effects

There are a few possible adverse events that might occur as a result of neutering a fully mature or senior dog.

  • Scrotal hematoma, swelling and pain
  • Failure of the surgical wound to heal quickly
  • Rough recovery from anesthesia

These can almost always be prevented with careful anesthesia, surgery and aftercare. Even if your dog has one of these complications, your veterinarian will be able to advise you on appropriate treatment.

Neutering is not expected to cause a major change for the worse in behavior even in mature dogs.

How Do I Know When to Get My Dog Neutered?

By neutering a dog at the time of puberty or shortly thereafter, the chances that they will engage in mounting, aggressive behavior, roaming and urine marking are much lower. Once a dog starts these behaviors, it’s less likely he’ll stop even after he is neutered. I have personally seen older male dogs who did stop urine marking after they were neutered, but it’s impossible to predict which ones will and which ones won’t!

The number one physical requirement for neutering a male dog with standard surgery is that his testicles have descended into his scrotum. This is usually complete by the time they’re 7 weeks old. Puppies can be neutered this young, but it’s rarely done so early. Most vets wait to neuter male pups until they’re at least 12-16 weeks old so they can tolerate anesthesia better.

Privately owned pups are usually neutered around 6 months of age. Letting them get a little older means they’re no longer such babies and can handle the surgery better. Doing surgery at this age usually prevents unwanted behaviors like urine marking and inter-dog aggression because the male hormones are not yet at their peak.

When is it too late to get a dog neutered? This senior dog can be neutered for health reasons.
Older dogs can be neutered if they have a disease made worse by testosterone.

What Happens If You Neuter a Dog Too Early?

One problem with neutering male dogs at 6 months of age or younger is it removes an important element of maturation. Sex hormones are important factors in both physical and behavioral development. Male dogs who are never exposed to these hormones never fully mature physically or mentally. You end up with a neutered dog who is, in some ways, a perpetual puppy. That sounds kind of neat, but is it really the best plan?

In 2007, a literature review (9) of available research in veterinary medicine found that early neutering increases the incidence of

  • Osteosarcoma
  • Hemangiosarcoma
  • Hypothyroidism
  • Obesity
  • Progressive geriatric cognitive impairment 
  • Prostate cancer
  • Urinary tract cancer
  • Vaccine adverse reactions 

Some dog breeds, specifically the Golden Retriever, are more susceptible to certain diseases like hemangiosarcoma, lymphoma and cruciate ligament injuries when they’re neutered early. (1)

One study found unspayed female Rottweilers were more likely to live a longer time than spayed female dogs. Of course, other studies argue that a neutered dog has less chance of early death due to infectious disease and trauma than an intact dog. (5)

Zlotnick et al. found that service dogs who were neutered at less than 7 months of age were more likely to be dismissed, mostly due to orthopedic problems. (12)

The interesting thing is that all of this is still very controversial. For every study showing that early neutering is detrimental, there is another one disputing the findings. 

The bottom line is that early neutering is probably a mixed bag of benefits and risks. You should discuss your dog’s unique needs with your veterinarian to decide the right time to neuter your male dog. 

What Is the Right Age to Neuter a Male Dog?

Neutering a male dog sometime between the ages of 9 to 18 months will usually ensure that they’ve entered puberty. A large breed dog tends to mature later than small and medium breeds, so they can be neutered at the later end of this range to allow their bones to finish growing.

If you have your dog neutered within a few months of him reaching hormonal maturity (6-12 months of age), you will most likely avoid unwanted behaviors related to male hormones. Even if he has started some behaviors like urine marking, it’s more likely he will stop after being neutered than if you allow the behavior to persist for years. 

Best Age to Neuter Popular Dog Breeds

Neutering after full maturity may help avoid some of the diseases associated with early neutering.

Small dogs tend to reach maturity younger than giant breed dogs. Closure of bone growth plates is one way to gauge physical maturity and this often occurs at about one year of age for most dogs but closer to two years of age in giant breed dogs. 

Below is a table summarizing the collected findings of Benjamin L. Hart, et al., who looked at other researchers’ findings on the effect of neutering age of different breeds’ tendency to develop diseases like cancer and joint problems. (3)

BreedRecommended Neutering Age
Australian Cattle Dog, Australian Shepherd, Bulldog, Cavalier King Charles Spaniel, Chihuahua, Collie, Dachshund, English Springer Spaniel, Great Dane, Jack Russell Terrier, Maltese, Miniature Schnauzer, Pomeranian, Toy Poodle, Pug, St. Bernard, Shetland Sheepdog, Shih Tzu, West Highland White, Yorkshire TerrierAge optional 
Cocker Spaniel, Corgi, Labrador RetrieverAfter 6 months
Beagle, Border Collie, Boston Terrier, Golden Retriever, Miniature Poodle, RottweilerAfter 11 months
Bernese Mountain Dog, Boxer, German Shepherd, Irish Wolfhound, Standard PoodleAfter 23 months


Neutering male dogs after the age of about 12 months may or may not improve unwanted behaviors like urine marking. Other benefits to neutering older male dogs include removing the hormone testosterone that contributes to diseases like benign prostatic hypertrophy and perianal gland tumors. 

There is emerging evidence that some dogs may have better health if they are neutered later than the current standard 6 months. If you’re concerned about when or whether to get your dog neutered, consult your veterinarian to determine the ideal time for your dog based on his breed, size, health risks and current behavior.

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  1. de la Riva, G. T., Hart, B. L., Farver, T. B., Oberbauer, A. M., Messam, L. L. M., Willits, N., & Hart, L. A. (2013). Neutering dogs: effects on joint disorders and cancers in golden retrievers. PloS one, 8(2), e55937.
  2. Dealing with concerns about pediatric spay/neuter. ASPCApro. (2020, October 27). Retrieved December 8, 2021, from 
  3. Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2020). Assisting decision-making on age of neutering for 35 breeds of dogs: associated joint disorders, cancers, and urinary incontinence. Frontiers in Veterinary Science, 7, 388.
  4. Hart, B. L. (2001). Effect of gonadectomy on subsequent development of age-related cognitive impairment in dogs. Journal of the American Veterinary Medical Association, 219(1), 51-56. 
  5. Hoffman, J. M., Creevy, K. E., & Promislow, D. E. (2013). Reproductive capability is associated with lifespan and cause of death in companion dogs. PloS one, 8(4), e61082. 
  6. Neilson, J. C., Eckstein, R. A., & Hart, B. L. (1997). Effects of castration on problem behaviors in male dogs with reference to age and duration of behavior. Journal of the American Veterinary Medical Association, 211(2), 180-182.
  7. Palestrini, C., Mazzola, S. M., Caione, B., Groppetti, D., Pecile, A. M., Minero, M., & Cannas, S. (2021). Influence of gonadectomy on canine behavior. Animals, 11(2), 553.
  8. Reisen, J. (2021, October 27). The most popular dog breeds of 2020. American Kennel Club. Retrieved December 8, 2021, from 
  9. Sanborn, L. J. (2007). Long-term health risks and benefits associated with spay/neuter in dogs. Erişim: http://www. naiaonline. org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs. pdf. Erişim Tarihi, 25, 2018.
  10. Schrank, M., & Romagnoli, S. (2020). Prostatic neoplasia in the intact and castrated dog: how dangerous is castration?. Animals, 10(1), 85.
  11. Waters, D. J., Kengeri, S. S., Clever, B., Booth, J. A., Maras, A. H., Schlittler, D. L., & Hayek, M. G. (2009). Exploring mechanisms of sex differences in longevity: lifetime ovary exposure and exceptional longevity in dogs. Aging cell, 8(6), 752-755.
  12. Zlotnick, M., Corrigan, V., Griffin, E., Alayon, M., & Hungerford, L. (2019). Incidence of Health and Behavior Problems in Service Dog Candidates Neutered at Various Ages. Frontiers in veterinary science, 6, 334.