Science on Pros and Cons of Neutering or Spaying Your Dog

Pros and Cons of Neutering or Spaying Your Dog

Table of Contents

Dog neutering or spaying—should I have my dog do it?

This might be one of the earliest questions we, responsible dog guardians, have thought of since we got our pups.

Are you hesitant to have your lovely pooch undergo this?

Yeah, me too. In the beginning, at least.

Many pet owners, including me, were given conflicting information on whether this is necessary, good, or bad for their dog's health.

And if you clicked on this article, you probably have the same questions as I had:

  • What are the pros and cons of neutering or spaying my dog? 
  • Should I leave my dog as nature has intended him/her to be?
  • What do dog experts and veterinarians think about this process?
  • Do all other dog owners spay or neuter their dogs?
  • What does science have to say about neutering or spaying your dog?

No, you're not overthinking.

These are all valid concerns of a responsible pet owner!

And I will try to address them with my personal experience, research evidence, and expert opinions.

After all, dog neutering is a grave decision you should not take lightly.

I also recommend listening to our Theory of Pet podcast episode on the pros and cons of neutering/spaying dogs and how people view this all-important surgery (below).


Dog Neutering Vs Spaying

Dog Spaying Pros and Cons

Dog Neutering Pros and Cons

Why Spay or Neuter Your Dog

Overview of Dog Neutering or Spaying: Should You Do It?

dog neutering, spaying a dog

Spaying and Neutering of Dogs: What Is It?

Let's start at the beginning to understand what spaying and neutering dogs really mean.

What does the surgery look like? And what does it entail for me and my pet?

Actually, many animals go through this, although they're most commonly used with dogs.

Both neutering and spaying refer to the most common sterilization methods, which vets call “de-sexing dogs” or “fixing dogs.”

Yeah, I know.

The term “fixing” a dog may be misleading or even ironic.

After all, the evidence on whether it should or should not be done is still inconclusive. More on this later.

So what is neutering?

Neutering is the de-sex procedure of male dogs where their testicles (or gonads) are removed.

The actual removal of a male dog's testicles is called Castration.

Then, what is spaying?

Spaying is a similar procedure of sterilization but for female dogs.

In this case, a female dog's ovaries and uterus are removed. It's called Ovariohysterectomy.

Neutering and spaying are used in veterinary medicine.

The term “neuter” will most often refer to removing reproductive organs in the dog for both sexes.

But colloquially, or in normal people's language, neutering doesn't necessarily apply to male dogs alone.

Before going into details about the pros and cons of these procedures for your pups, let's take a look at what science has to say about neutering and spaying.

Dog Neutering and Spaying: What Do Science and Experts Say?

dog castration

Most veterinarians, experts, and state laws consider neutering or spaying your dog necessary.

Actually, it has been like this for decades.

Well, that means good, right?

Uhm, sure.

But you must also know that there's recent research that questioned this surgical procedure.

Many studies have been coming out over the last five years showing how neutering and spaying dogs may actually be not that good for our dog's health.

Science-Based Overview

Here's a quick science-based overview of what we know today:

  • Early dog neutering doubles the chance of hip dysplasia (1)
  • Early dog neutering increases joint disorders in dogs by four times (2)
  • Neutering dogs triples the risk of several joint problems in GSDs (3)
  • Neutering decreases longevity in Rottweilers (4)
  • Neutering increases the chance of cancer in dogs (5)

Pretty worrying, right?

With this new research and more on the horizon, vets and scientists are beginning to reconsider their stance on neutering and spaying dogs.

However, in general, these studies are still not conclusive and require more biological research.

One thing is clear, however:

We must definitely reconsider the time of spaying and neutering dogs.


Because based on all the scientific data, it is clear that early neutering has more cons than pros.

Apparently, spaying or neutering your dog much too early will likely cause them joint disorders, obesity, and even cancer.


“In addition to dogs suffering pain from joint disorders, the condition may also disqualify the dog as a working partner in military and police work. We hope these findings provide evidence-based guidelines for deciding the right age to neuter a puppy to reduce the risk of one or more joint disorders.”

– Prof. Benjamin Hart, UC Davis School of Veterinary Medicine

So with all we've learned above, you shouldn't really rush into spaying or neutering your dog.

But don't feel discouraged and close this article just yet!

There are also advantages to this procedure.

Some are even based on scientific research, while others still do not have conclusive evidence.

Historically and statistically speaking, there used to be more pros than cons to this.

So currently, vets still highly recommend the surgery for various reasons.

But to help you decide, let's take a look at the general agreement on the pros and cons of spaying and neutering dogs.

RELATED: How Neutering Dogs May Lead to Cognitive Impairments

Dog Spaying: 3 Pros and 3 Cons
(Female Dogs)

Pros of Spaying Your Dog

Pros of Spaying a Dog

PRO of spaying your dog: Heat Period Reduction

Dog spaying will prevent periods of your baby girl being in heat.

As you know, when a female dog is in heat, her genitals swell.

She lets out a scent that can be traced for up to a mile and attracts unwanted attention from male canines.

Before having my female spayed, she used to escape the house and wander around the neighborhood.

It was stressful!

But after getting the operation, her escape artistry mellowed down.

When your girl is spayed, she will also have less desire to wander and look for a mate.

And… I don't know about you, but I definitely don't miss the bloody discharge I often find on my sofa.

Spaying your female will also prevent that!

And the cherry on top?

Vets attest (and so do I!) that your dog will be a much cleaner, calmer, and more affectionate dog.

Dog Spaying

PRO of spaying your dog: No Doggy Pregnancy

This may be obvious, but spaying a dog prevents your female canine from getting pregnant.

Whether intentional or accidental, dog pregnancy can be expensive and time-consuming.

Not only that, but it also comes with health risks and responsibility for your pooch!

Also, dog pregnancy equates to soaring vet bills.

Dog food, vitamins, and other supplies for dog care definitely can definitely dent your pocket.

Also, any complications that may happen will result in even more vet care bills.

There's a small risk of death of the mama and/or the newborn pups.

So if you come to think of it… you won't have to go through all the expenses and possible risks if you prevent pregnancy by spaying your female dog.

PRO of spaying your dog: Less Risk of Cancers

Now, don't think you're being selfish by spaying your dog.

It won't just benefit you but her as well!

Spaying will prevent the risk of cancer in your dog's uterus, ovaries, and reproductive tract because the organ will be removed.

It can also save her from breast cancer, especially if she gets it before she reaches 2.5 years old.

And also, spaying can protect your dog from uterine infections.

It's been observed that one in four unspayed female dogs will contract a uterine infection. If left untreated, this disease may very well kill your pet.

But aren't these cancers and infections already uncommon for female dogs?

Well, yes, actually.

But even vets say it's still a valid reason to spay your dog.

It doesn't hurt to be safe!

READ: 15 Tips on Dog Pregnancy and Whelping

Cons of Spaying a Dog

CON of dog spaying: Hypothyroidism and Weight Gain

To be fair, spaying your dog is not all hearts and flowers.

One of the more known side effects of spaying your dog is the risk of hypothyroidism.

Low thyroid levels in a female canine will result in weight gain and obesity, which is difficult to fight even with an adequate diet.

Your dog may also become lethargic and tired and start losing hair.

I did notice this in my dog but only during the first few weeks after the operation.

Veterinarians recommend special medication to deal with hypothyroidism in dogs.

This condition may be why your dog is gaining weight.

And eventually, you might need to start dealing with dog obesity.

A spayed dog often starts gaining weight at an increased rate after the procedure, most likely due to changes in her metabolism and hormonal structure.

Can this be prevented?


What I did with my dog was daily exercise outside. We either walk to the park or run every morning.

I also talked to my vet about my dog's nutrition and proper food intake.

Those are enough to prevent her from being overweight.

CON of spaying your dog: Cancers and Complications

I know I've presented scientific evidence above about how spaying can save your dog from specific cancers.

But on the flip side, this procedure could also increase the risk of other deadly canine cancers, like lymphoma and hemangiosarcoma.

Hemangiosarcoma disease, in particular, affects the dog's spleen and heart.

These vital organs are normally protected by your female canine's reproductive organs (which are removed in spaying.)

And not to mention that if the surgery is done wrong or at the wrong age, more health complications can be expected.

Not to scare you, but some complications that might happen are:

  • uneven bone growth
  • bone cancer
  • urinary incontinence
  • affect the appearance of her private parts

And other things to consider are that the abnormal vulvas can trap bacteria and cause dermatitis, vaginal infections, and urinary tract infections.

CON of spaying your dog: Sterilization and Use of Anesthesia

Depending on your perspective, sterilizing, a.k.a. your dog never getting pregnant, may be good or bad.

There's no going back from this!

But given the overpopulation of dogs, with millions being stray, homeless, living in shelters, or being euthanized, this might be a good thing, especially for pet advocates.

Also, this procedure uses general anesthesia.

Although it didn't happen to my dog (thankfully,) there's a possibility that your pet will react poorly to this.

Some studies suggest about 1 in 5 dogs will have complications after surgery under general anesthesia.

But don't fret!

Most of these complications are not serious health issues and have a meager death rate.

RELATED: 30 Myths That Many Dog Owners Still Believe

Dog Neutering: 3 Pros and 3 Cons
(Male Dogs)

Pros of Dog Neutering

Pros of Neutering a Dog

PRO of neutering your dog: Reduction of “Male Behavior”

We have an alpha male in the pack who always gets aggressive with the other males when he's in heat.

He won't eat and will only follow the females around while whining.

When not in heat, he's sure an adorable and playful dog. Except for the constant marking of territory.

If your dog does these, too, then neutering will reduce this “male behavior.”

Reduce Aggression

To be more scientific about it, neutering will reduce any dog's aggression because it involves removing the main source of their testosterone.

This can mellow out your male dog, according to research.

It also means neutered canines tend to be more affectionate and gentle.

And not just with their humans, but with other pets, too!

They're less likely to get into fights with other animals, saving you stress and vet bills in case of injury.

Reduce Sexual Desires

Of course, neutering a dog will reduce your male dog's sexual desires.

He is less likely to hump other pets or objects.

It will also keep your male from chasing a female in heat.

When my dog was neutered, he stopped humping his teddy bear.

He also stopped getting agitated when we passed by female dogs.

This helped prevent him from escaping and following around a female's scent (which has happened quite a lot before.)

Neutering a dog

PRO of neutering your dog: Better Prostate Health

Not only does neutering alter their “male behavior,” it could also benefit your dog's health!

Based on previous research, experts say it can also prevent prostate problems and improve testicular health.

One study says prostate problems can occur in 80% of non-neutered males.

However, another study has shown that castration may actually increase the progression of tumors.

Sometimes, male dogs get a skin disease known as perianal fistula or anal fistula.

This nasty condition develops carbuncles around your dog's anus and is often very complicated to treat.

But if neutered, the risk is highly reduced.

Testicular cancer can also be eliminated by neutering.

Even though only 7% of non-neutered males get testicular cancer, neutering your male dog removes the risk.

PRO of neutering your dog: Control of Breeding

Finally, neutering keeps your dog from breeding.

Many pet advocates, veterinarians, experts, humane societies, and lawyers agree that this benefit outweighs all risks.

Plus, if your dog sired puppies, you won't know how the pups are being treated.

And if you choose to help raise them, puppy pet food and vet care bills are quite costly, too.

Also, you would have no idea how the new puppies are being treated or if they are safe.

Cons of Neutering a Dog

CON of neutering your dog: Hypothyroidism and Weight Gain

Just like spayed female dogs, neutered males can also get hypothyroidism, which studies have shown, triples the risk of obesity.

Once castrated, a male dog's endocrine system starts to function differently.

His hormonal levels are affected, including lower thyroid levels.

This results in very rapid weight gain and dog obesity.

But hypothyroidism can be treated, can it not?

Of course.

Ask your vet about how to treat it properly in case diagnosed.

You can also address your dog's weight gain separately with the help of your vet.

What I do with my dogs is get fussy about their meal quantities.

Our vet also advises putting them on a weight-loss diet, using low-calorie foods and healthy dog treats.

That's, of course, on top of their daily exercise (which does wonders for me, too!)

CON of neutering your dog: Dementia and Bone Problems

Statistically, geriatric cognitive impairment or canine dementia is common among neutered dogs.

If this happens, your dog will start forgetting things he used to know.

He'll be disoriented wherever he is, even if it's the house where he has lived for years previously.

Just like human dementia, dogs will also interact differently and forget the obedience training he's gone through.

Also, if the neutering was done poorly or performed too early in a dog's life, there's a possibility of hip dysplasia, ligament problems, and even osteosarcoma, as the studies above mentioned.

Apart from testosterone, a male's reproductive organs also release hormones that help develop the body parts associated with these diseases.

So removing their organs will naturally lead to these possibilities.

CON of neutering your dog: Risks of Anesthesia

Again, same as spaying your dog, neutering means that your pet will have to undergo surgery requiring anesthesia.

This means there's a chance that your male canine will react poorly to anesthesia itself.

As previously indicated, 1 in 5 dogs may have health complications after surgery under general anesthesia.

But these complications will not be very serious, with a meager death rate.

Spay or Neuter Dog Graphic

Why Spay or Neuter Your Dog

spaying a dog

Still undecided?

Here are the most commonly cited reasons for neutering that might seal the deal for you (or your dog.)

  1. Control the population growth of dogs;
  2. Eliminate or decrease the chance of a dog developing certain types of diseases.

Overpopulation of Dogs

In North America, most animal shelters, veterinary clinics, and humane societies highly recommend (a.k.a. force) pet owners to spay or neuter their dogs to prevent further problems to an already huge overpopulation of domestic animals.

Some states are even legally required to spay or neuter dogs before they can be adopted.

This problem is real.

The Humane Society of the United States cites that more than 6 million pets are brought to animal shelters every year:

Number of dogs in the United States
Several dogs in the United States. Credit: Humane Society

The number of domesticated pets in the US is growing, as is the number of animals brought into shelters.

Because of this, dogs are the most common recipients of this surgical procedure.

Dog owners will usually have their puppies spayed or neutered around the age of 6 months or earlier.

Neutering and spaying of dogs are done under general anesthesia, so your canine won't feel a thing when a surgical incision is performed.

If you're curious as to what you can do before or after the surgery, read on to our next section.

How to Prepare Your Dog Before Spaying or Neutering

Before the surgery, your vet will typically want to confirm that your dog is healthy.

Your dog will also typically have to fast before the surgery to prevent nausea from the anesthesia. 

What to Pay Attention to and Expect After the Surgery

Your vet will ask you to restrict your dog’s activity for 7 to 10 days after the surgery.

Expect your dog not to eat as much the first day after surgery, but this should quickly change.

You will have to bring your dog back in a week or two, so the vet can remove the stitches and check the incision.

My dogs, when spayed and neutered, took about more or less 2 weeks before they fully recovered, so you can expect the same with your dog.

LISTEN: Podcast on Pros & Cons of Neutering/Spaying Dogs

FAQs About Dog Neutering or Spaying

If you still find yourself wondering what to do, consider the following questions and answers. 

Do Female Dogs Change After the Spaying Procedure?

It is common for female dogs to have more consistent behavior after doing the procedure.

This comes from the lack of hormonal changes associated with their cycle. 

What Age Should a Dog Do the Procedure?

Most experts agree that you should spay your dog at around four to six months old.

In some situations, your vet may suggest doing so earlier or later. 

How Long Does It Take a Dog to Recover From Being Spayed?

On average, the incision from neutering or spaying your dog should heal around 10 to 14 days. 

What Happens When You Spay a Female Dog?

Spaying a female dog means removing her reproductive organs.

The procedure always removes her ovaries and typically also removes the uterus.

Neutering is the term used to describe removing the reproductive organs of a male dog. 

Do Dogs Bark Less After Spaying?

It is common for dogs to bark less after being spayed or neutered.

They may also have reduced aggression and do not wander as much.

This comes from the reduction in activity that is typical after the procedure. 

Is there a Reason to Spay Your Dog Other Than to Prevent Pregnancy? 

Your vet may also suggest spaying your dog to treat phantom or false pregnancy, abnormal cycles from ovarian cysts, cancer, or uterine infections.

It may also be part of your dog’s diabetes treatment.

Dog Neutering and Spaying: Before You Go…

Now that you've taken a look at all the pros and cons of spaying and neutering, it's up to you to decide whether you'll have your fur baby undergo this.

Obviously, we still need more conclusive evidence on how to view this procedure and whether it's essential to fix your dog.

In my opinion, as someone who decided for it for my dogs, it seems that it's still worth the risks in return of the benefits we gained.

But that said, the most important thing to keep in mind is to do it at the right time.

Concerning yourself with the pros and cons of neutering a dog while your pet is still a young puppy is a good way to plan, but not rush into that.

Whatever you decide on, I'm sure your pup will just be overjoyed that you're there to look out for his overall welfare.


Click here to see study citations and references

Footnotes, study citations, and further reading:

  1. Torres de la Riva, G., 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. Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2014). Long-Term Health Effects of Neutering Dogs: Comparison of Labrador Retrievers with Golden Retrievers. PLoS ONE, 9(7), e102241.
  3. Hart, B. L., Hart, L. A., Thigpen, A. P. and Willits, N. H. (2016), Neutering of German Shepherd Dogs: associated joint disorders, cancers, and urinary incontinence. Vet Med Sci, 2: 191–199. doi:10.1002/vms3.34
  4. 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.
  5. Zink MC1, Farhoody P, Elser SE, Ruffini LD, Gibbons TA, Rieger RH. Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas. J Am Vet Med Assoc. 2014 Feb 1;244(3):309-19. DOI: 10.2460/javma.244.3.309.
  6. Patnaik AK1, Greenlee PG. Canine ovarian neoplasms: a clinicopathologic study of 71 cases, including histology of 12 granulosa cell tumors. Vet Pathol. 1987 Nov;24(6):509-14.
  7. Pollari, F. L., & Bonnett, B. N. (1996). Evaluation of postoperative complications following elective surgeries of dogs and cats at private practices using computer records. The Canadian Veterinary Journal, 37(11), 672–678.
  8. Pollari FL1, Bonnett BN, Bamsey SC, Meek AH, Allen DG. Postoperative complications of elective surgeries in dogs and cats are determined by examining electronic and paper medical records. J Am Vet Med Assoc. 1996 Jun 1;208(11):1882-6.
  9. Heidenberger E1, Unshelm J. [Changes in the behavior of dogs after castration]. Tierarztl Prax. 1990 Feb;18(1):69-75.
  10. Bryan JN1, Keeler MR, Henry CJ, Bryan ME, Hahn AW, Caldwell CW. A population study of neutering status as a risk factor for canine prostate cancer. Prostate. 2007 Aug 1;67(11):1174-81.
  11. Teske E1, Naan EC, van Dijk EM, Van Garderen E, Schalken JA. Canine prostate carcinoma: epidemiological evidence of an increased risk in castrated dogs. Mol Cell Endocrinol. 2002 Nov 29;197(1-2):251-5.


Neutering or Spaying Your Dog

Jennica has a degree in clinical psychology and has many years of experience as a staff writer for different scientific publications, both online and print. She's an avid writer with an interest in exploring the relationship between humans and dogs using scientific research.