Dog Neutering Overview: What to Do & When

Updated January 6, 2022
puppy at veterinarian office

If you have a male dog you're not planning to breed or show, chances are you're considering having them fixed. Doing so has numerous benefits, but at what age you have the procedure done can have an impact on your dog's health and wellbeing. Experts have released updated recommendations for the best time to neuter a dog based on one important factor: their size. In general, smaller dogs should be neutered at 6 months of age, and larger dogs should be neutered between 9 and 15 months.

Determining the Right Age to Neuter

You've probably heard several different answers to the question of when to neuter your dog. This isn't surprising, considering experts have long debated the topic.

Unfortunately, there's still no magic number, but emerging studies suggest that the size of a dog (and not necessarily their breed, as previously believed) could be the most important factor used to determine whether early neutering is safe or if it's better to wait. According to the American Animal Hospital Association (AAHA), the following are the most current guidelines.

  • Smaller dogs (those with an adult weight under 44 pounds) should be neutered at or before 6 months of age.
  • Larger dogs (those with an adult weight of 44 pounds or more) should be neutered between 9 and 15 months of age or older based on when their growth stops.

These recommendations are based on extensive research, but most recently a study done by the University of California, Davis, involving various sizes of mixed-breed dogs. Their findings suggest that larger dogs who were neutered within their first year of life had increased incidence of joint disorders. This is likely because larger and giant breeds of dogs take longer to mature and grow, so many veterinarians now recommend delaying neutering until the dog's growth plates have closed. The smaller dogs in the study did not have the same increased risk.

Here's the tricky part: if you don't know your dog's breed or the size of their parents, it can be challenging to estimate their adult weight. Fortunately, you can use a puppy size calculator to get an approximate guess or ask your veterinarian. And if you have no idea what age your new pup is, consider their characteristics to guestimate.

Behavioral Reasons for Early Neutering

Bernese puppy sitting on grass

There are several reasons why someone might elect to have their dog neutered before they reach sexual maturity. Neutering dogs at an early age can help prevent some dogs from developing negative behavior patterns.

  • Aggression: Some males exhibit aggressive behavior once they become sexually mature, so neutering before they reach maturity could prevent it.
  • Marking: Territorial marking can be another problematic issue that may occur in dogs who haven't been neutered.
  • Roaming/Escape: Dogs past sexual maturity are more likely to escape confinement and roam the neighborhood, which can lead to fighting or injury.

In some cases, early neutering can prevent these types of behaviors from becoming part of a dog's nature. However, it is not guaranteed to fix or eliminate all possible behavior problems. Proper training is the best deterrent for unwanted behaviors.

Concerns About Neutering Too Early

Alternatively, many people are concerned that if they have their dog neutered too soon, the procedure will have a negative impact on their personality and physical development. While some of these concerns are based on myth, others may have some truth to them.

Changes in Personality

There is a long-running myth that neutering male dogs will cause them to stop being playful companions. While neutering can have an effect on your dog's behavior, especially if neutered young, how they will mature really depends on your individual dog, their breed, and environment. It may also reduce aggression toward other dogs in cases where these issues are already a problem, or the potential is there.

Joint Problems

Evidence points to the belief that large breed dogs (and larger mixed-breed dogs) can develop issues with their musculoskeletal system when neutered too early. As a result, your dog could be more likely to experience painful conditions like ligament tears, hip or elbow dysplasia, and knee injuries. However, there's also evidence that neutered dogs are more likely to experience these joint problems compared to those who are intact (not neutered).

Increased Risk of Cancer

Similar to the research on joint disorders, data suggests that neutering dogs can increase their risk of developing numerous types of cancers. That's not to say that a neutered dog will get cancer, but they could be prone to certain cancers, such as lymphoma, hemangiosarcoma, and mast cell tumors.

Early Neuters in Shelter Dogs

In addition to the behavioral reasoning behind early neutering, shelters tend to perform the surgery when dogs are very young out of necessity. They're done in an effort to keep the homeless pet population down. The mindset behind this is that it's usually more practical and effective for a shelter to adopt out an already fixed pet rather than relying on the owner to return for the surgery at a later date.

Even though neutering at such a young age is still somewhat controversial, it isn't necessarily risky. Some organizations, including the American Society for the Prevention of Cruelty to Animals and American Humane, report that spaying and neutering can safely occur as early as 8 weeks old.

Male puppies usually have both testicles descended by this age and can tolerate the anesthesia. Young dogs also heal more rapidly than older pets, so their recovery time is reduced. Data suggests that early spays might have more long-term consequences versus neutering in males, but the relationship is still being investigated.

If your rescue pup was neutered in the shelter at a very early age, there's no need to panic. Just continue providing them with optimal care, keep them at a healthy weight, and report any concerning behaviors or symptoms to your veterinarian as soon as you notice them. Your dog can still live a long and full life.

Pros and Cons of Fixing a Male Dog

Breeders, veterinarians, shelters, and rescue groups will all have varying viewpoints on whether it's best to neuter a dog or not. If you're on the fence about the procedure, it can be helpful to consider the pros and cons of neutering.


  • eliminated risk of testicular cancer and lower incidence of prostate disease
  • helps to reduce the population of unwanted puppies
  • possible reduction of behaviors such as marking, roaming, and some types of aggression
  • lower risk of perineal tumors and hernias


  • higher incidence of bone, urinary tract, and prostate cancer, as well as hemangiosarcoma and other cancers
  • possibly increased risk of becoming obese
  • higher probability of bone and joint disorders, such as hip dysplasia

Neutering an Older Dog

adult dog at veterinarian office

What if your dog is older than 6 months of age or even several years old and you are thinking of having them neutered? There is no age that is "too old" for your dog to be neutered, but adult and senior dogs do have some special considerations.

Older dogs are more likely to have complications after neutering, such as swelling and bleeding into the scrotum, increased pain, or impaired healing. Senior pets are also more likely to have heart disease, kidney disease, or other illnesses that could make anesthesia riskier. Pre-surgery screening, including blood work, EKG, and X-rays, can help make the procedure as safe as possible. How and when to neuter an older dog should be decided on a case-by-case basis with your veterinarian depending on your individual dog's health.

Seek Expert Advice

Fortunately, your veterinarian can help you make an informed decision about the best age to neuter your special pet. When you take your puppy to the vet for vaccines and an exam, discuss your concerns about the benefits and risks based on their breed, size, and health condition. Whether your dog is a purebred or a mixed-breed, your veterinary health professional is the best resource for all healthcare information.

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Dog Neutering Overview: What to Do & When