golden retreiver staring at camera

Why and When to Neuter a Dog

Spaying and neutering are terms that have become pretty commonplace in our society. Spaying and neutering pets has been advocated by shelters and rescue groups for years.

But in practice, I find that many pet parents know much less about what spaying and neutering entails than I might have thought. There are actually a lot of factors to consider when it comes time to spay or neuter, not the least of which is at what age to do it.

In this article, we’re going to discuss what spaying and neutering actually are and why they’re different, why spaying and neutering are recommended, and finally, when it’s the best time to spay or neuter your dog.

black pug puppy sits wearing a cone around head

What are spaying and neutering?

Spaying and neutering are both procedures that involve removing the reproductive organs of an animal. In almost all cases, these are surgical procedures, and can only be performed by licensed veterinarians who have the training to perform them properly and safely. While the term neutering can technically be applied to both as a general term, spaying refers specifically to females, and neutering is referred to more specifically for males.


The medical term for spaying is ovariohysterectomy, with the abbreviations OHE and OVH often used.

A spay procedure involves surgical removal of the uterus and ovaries, which are both required for reproducing and having puppies.


The medical term for neutering is orchiectomy, with the abbreviation OE sometimes used. But more commonly, even doctors just refer to this procedure as neutering.

Neutering involves surgical removal of both testes, which as producers of sperm, are required for reproduction on the other side of things.

Why Neuter a Dog? It sounds scary, right? And uncomfortable. Why put your pup through it at all?

Well, the first thing to remember, is that thousands of spay and neuter procedures are performed everyday without incident. This is because in an overwhelming number of cases, these procedures are performed in young, healthy dogs.

These are procedures that even new graduate veterinarians are expected to be capable of doing prior to graduating from veterinary school, so even your youngest, newest vets should have the knowhow and experience to perform them safely and successfully.

The next thing to know about are the numerous benefits to spaying and neutering.

Improve Undesireable Behavior

Reproductive organs are responsible for producing certain sex steroid hormones, like testosterone and estrogen. Thus, by removing those organs and the hormones they produce, we can see a change in behaviors associated with those hormones.

This is most prominently the case with neutering male dogs. Male dogs stereotypically show signs like dominance and territorial aggression, but this isn’t with all our male pups. It’s a mistake to assume that all intact male dogs are mean, because most aren’t.

But even the friendliest male dogs may not be able to resist climbing up your neighbor’s leg and going to town, or urinating in an inappropriate (or embarrassing) place to mark their “territory” where another dog has been.

Neutering can improve or even resolve some of these behaviors. But it’s also important to remember that it won’t correct any and all undesirable behaviors. That’s why it’s also extremely important to train and socialize dogs from an early age.

Reduce Roaming Behavior

This is a very important benefit and perhaps the most important when thinking about a dog’s welfare. According to the American Humane Society, 1 in 3 pets will get lost in their lifetime.

A leading cause of pets that are not neutered actually getting out of the home and wandering off is because they’re seeking out members of the opposite sex.

I’ve heard of intact male dogs breaking fences, digging holes, or plowing through screen doors to reach a receptive female in heat that they’ve caught a whiff of. But males aren’t the only ones. Many years ago, my own uncle’s intact female Bichon escaped from their home for 2 days. Roughly 2 months later, she had a litter of 4 puppies.

Roaming behavior puts pets at a high degree of risk, including being hit by cars, fights with other roaming dogs, being picked up by animal control, or theft. And while having a microchip does dramatically increase the likelihood that a lost dog will be returned, the return rate is still just over 50% according to AHS.

Reduce the Population of Homeless Pets

According to the ASPCA, about 6.5 million animals enter United States shelters, with about half being cats and half being dogs. Of the 3 million dogs that enter shelters, about 700,000 of them end up euthanized.

The number of “kill” shelters has gone down a lot over the past few decades, but there’s still many county shelters that do euthanize dogs and cats, as they simply don’t have the capacity to handle the sheer number of stray dogs and cats that are out there.

And while the “no kill” movement is well-intentioned, many of these dogs are simply never adopted or may not even be adoptable, leading to a rising number of homeless dogs. The most common reason a dog is relinquished or abandoned? Unwanted behavior or aggression. Unfortunately, by 1 year of age, most of those behaviors are permanent and simply can’t be corrected, and a lot of stray dogs are pretty close to that age or older.

So, because finding homes for literally millions of dogs a year simply isn’t realistic, spaying and neutering is probably the kindest and most proactive preventative action we can take against millions of dogs ending up stray and homeless, and possibly being euthanized.

black lab waits outside a dirty storefront

Preserving Public Health (For You and Your Dog)

But you might ask yourself, why is it so important for dogs to be in a shelter or home? Can’t they just live out their lives in the wild? The simple answer is no, they can’t.

While tens of millions of cats live in outdoor feral or stray cat “communities” that are monitored by volunteers, this simply is not acceptable for dogs. Colonies of cats tend to remain largely out of the public eye and tend to hide if approached by people. But imagine a pack of feral dogs roaming around your neighborhood and the kind of health and safety risks that poses.

About 55,000 people die from rabies each year, and this is predominantly in countries that have poor rabies vaccination protocols in place, limited neutering capabilities, and lots of stray dogs and cats roaming the countryside.

There’s also a greater risk of fatal diseases like distemper virus, parvovirus, and leptospirosis, that can be spread between dogs and wildlife like raccoons and coyotes. Leptospirosis can be transmitted to people through contaminated urine.

And most of your feral cats can be easily, safely, and humanely trapped, neutered, vaccinated, and returned to their colonies. This simply isn’t practical for dogs.

So while population control may sound harsh, it can be done safely and humanely, while the alternatives of disease spread and the premature ending of an otherwise healthy animal’s life are far more grim.

Reduce Risk of Cancer and Other Medical Conditions

Lastly, there are several health benefits we can see from spaying and neutering.

Practically Eliminate the Risk of Breast Cancer

Studies have shown that spaying a dog before she has her first heat cycle will just about eliminate the risk of developing mammary cancer, which in many dogs winds up being fatal.

Dogs that don’t die from breast cancer, still have chronically painful ulcerated growths that permanently remain so unless surgically removed. And surgery for these dogs is very intensive and the recovery is painful too.

Dogs most often have their first heat cycle between 9 months and 15 months of age, and many dogs only go into heat once or twice a year. Spaying before this first heat happens just about eliminates your risk. Waiting until after the first cycle but before the second increases the risk by only about 5%. Waiting until after the second but before the third raises the risk to about 25%. It only continues to go up from there.

Preventing Pyometra

A pyometra is a life-threatening infection of the uterus, where the organ fills up with inflammatory, bacteria-laden fluid. After only a couple days, the uterus can fill up to the point that it may rupture, leading to a serious body system wide infection that most dogs do not survive.

This condition can only happen in female dogs with a functional reproductive tract, and largely occurs secondary to hormonal influence, not so much from a transmissible infection that a dog “gets” from somewhere. The period shortly after a dog’s heat is finished, called the diestrus phase of the cycle, is the time when this occurs.

Removing the reproductive tract completely eliminates this terrible condition from occurring. If a pyometra occurs, surgery is possible, and is in fact the only viable course of action to take, but these poor dogs are often extremely sick, making them risky anesthetic patients. The uterus is also very fragile in this state and can rupture at any time during surgery, even when delicately handled by the surgeon.

Eliminating Testicular Cancer

Approximately 30% of intact male dogs will develop testicular cancer. While some cancers, like interstitial cell tumors and seminomas, respond well to treatment by neutering alone, there are others that have a higher rate of metastatic spread and invasiveness, where even removing the affected testis through neutering is not enough to clear the disease.

But as you might imagine, all of these can be completely prevented by neutering early in life.

Protecting Prostate Health

Male dogs have a prostate, just like human men do. And just like human men, intact male dogs can develop benign prostatic hyperplasia (BPH) where the prostate gets abnormally large. But unlike men, there are not really many good medical options available for treating BPH. Neutering is still the treatment of choice for dogs.

BPH may also sound like a harmless enough thing, but it’s really not. The prostate becomes very large, as the name implies, putting pressure on the urinary tract and colon, making it difficult for affected dogs to eliminate normally.

Some dogs with BPH will develop extremely large fluid-filled cysts that lead to bloody urine and pain. I once had a canine patient with BPH with a cystic prostate that had filled up to the size of a grapefruit.

Intact dogs are also at a much higher risk of prostate infections and abscesses. Treating these tends to be very expensive and time-consuming, often costing several hundred dollars and several weeks of antibiotic treatment. Sometimes, these infections may not even resolve without neutering.

For further reading on these topics of neutering benefits, be sure to check out our article Why Spay or Neuter Your Dog or Cat? Here’s 5 Important Reasons.

When to Neuter a Dog

We’ve discussed the “why” pretty thoroughly. And in most cases, new pup parents in the US are more than willing to neuter their pooch, because this has been a standard recommendation for many years.

But something that has changed a little is the time at which we recommend doing a spay or neuter procedure, because it can be different depending on a dog’s breed and expected adult size.

In the last few years, there has been some well-published data on Golden Retrievers, German Shepherd Dogs, and Labrador Retrievers, that has pointed to a higher incidence of certain diseases if they are “fixed” before they reach full skeletal maturity.

Most of these conditions are related to orthopedic disease and certain types of non-reproductive cancers. For example, the Morris Animal Foundation launched the Golden Retriever Lifetime Study in 2012. The goal? Take one of the most popular dog breeds in the US and see what risk factors led to certain types of disease conditions.

The study is still ongoing, but findings after just one year of the study showed some alarming results, that started to change thinking about the mandate to spay or neuter dogs as early as possible, a common practice and requirement by shelters and rescues.

It was found that the incidence of hip dysplasia, a commonly feared orthopedic disease in large breed dogs, was about double in early-neutered male dogs compared to their intact counterparts. And in both males and females, cruciate ligament tears (the often-feared “ACL” tear) was also higher in dogs spayed or neutered at only a few months of age.

Increased risks were also seen for 3 types of cancers, including mast cell tumors, lymphosarcoma, and hemangiosarcoma.

Confusion still remained about how much of these results were purely from spaying and neutering, and how much was due to genetic predispositions for certain dog breeds for certain diseases.

Compounding this confusion still, is that there is a wealth of data on very few dog breeds and there are countless dog breeds and dog breed mixes out there. What does the Golden Retriever Lifetime Study mean for a Dachshund? What are their risks?

But regardless, these findings started to change the thought process about timing for when to neuter a dog. We now find ourselves as doctors and pet health advocates trying to find some kind of balance between the benefits of neutering and preventing certain types of cancers, and avoiding neutering to avoid other diseases and other cancers.

For example, if I see a Golden Retriever puppy, I have a serious discussion with the parent about the risks Golden Retrievers can face if spayed or neutered too early and about how these risks can be mitigated by waiting until the pup reaches full skeletal maturity. However, I also have to discuss that waiting later can increase other risks and that we need to find the right balance.

So what’s the compromise? Well, we know that dogs reach skeletal maturity at different ages, based on how large they are. A chihuahua for example, reaches full growth at less than a year, while a Great Dane doesn’t reach the same level of growth for nearly two years.

Because we know that the risk for breast cancer still stays low between the first and second heat cycle and that the first heat cycle for most dogs won’t happen until 9-14 months of age with the second not occurring for months after, we try to plan a spay procedure for large breed dogs somewhere after they reach full skeletal growth and before their second heat cycle.

For your average Golden or Lab, this is often around 14-15 months of age, maybe a little later if the first heat cycle occurs later. For your male dogs, this is a little easier since we don’t have the time constraint of heat cycles. But the older a male dog is, the harder and more difficult the neuter procedure and recovery can be. Any vet can regale you with frustrating stories of neutering older dogs. There’s more bleeding, swelling, and the procedure just takes longer. Thus, even without the constraint of a heat cycle, neutering around the same time at 14-15 months of age for the boys is often advised.

Now what about a small dog, like that Chihuahua, a Bichon, or a Jack Russel? Or how about a medium-sized breed like an Australian Shepherd, a Border Collie, or a Beagle? We don’t have data for these breeds but we know they reach their skeletal maturity earlier. So, we can probably still stick with spaying or neutering around 7 or 8 months, before the first heat cycle for girls, and before things get too tough and complicated for the boys.

It’s also important to think about timing based strictly on age and the risk a dog has for developing concurrent diseases. Would I rather neuter a 7 year-old dog with prostate disease, arthritis, and early liver value changes making him a riskier surgery candidate requiring a 45 minute procedure? Or would I rather have neutered the same dog at 7 months before he had prostate disease or any labwork abnormalities and neutering would have only taken 15 minutes? If hindsight was truly 20/20, the decision would be easy.

But unfortunately, 20/20 hindsight doesn’t exist, so all we have is risk/benefit analysis, and hoping that more studies are available in the future that give us more information to help with recommendations.

black pug puppy sits with a sad stare

Your Pup is an Individual

All this data we have is all well and good. And perhaps your pup is a Golden Retriever, where the recommendations are more clear based on the data we have. But chances are, you don’t have one of the few breeds where a wealth of data exists.

Because dogs come in all shapes and sizes, and there are many lovable breed mixes out there, we don’t want to treat them like a statistic. If you have questions about when the best time is to spay or neuter your pooch, make sure to have this discussion with your own vet. He or she can help develop a plan based on specific risks and benefits, which can then be catered to your individual pup.