Should you neuter your dog?

Dog neutering was once an almost automatic procedure for pet dogs. Vets routinely desexed puppies around six months of age, though sometimes as young as seven weeks. It still happens. 

These days, though, more and more vets acknowledge it’s better to wait until the dog is as old as possible before removing their sex organs — or ideally, avoid neutering altogether.

My breeder recommended waiting until my pup was at least 12-18 months old. Why? So the bone plates would be fully formed before we interfered with the testes. The testes (and ovaries) produce hormones that play multiple functions in the body. 

But even my breeder was only half right.

This post is for general informational and educational purposes only. I encourage readers to see my full disclaimer here.

After scouring the literature to find all the information I could on what impact neutering has on a dog’s health, I decided against ever desexing any dog of mine. Which makes me unusual where we live.

I still cop consternation and mild disapproval from other dog owners when they notice my dog is intact. Not to mention from the odd vet. Desexing has long been equated with responsible dog ownership.

For many owners the only questions around dog spay and neuter are when to neuter a dog and how much does it cost to neuter a dog? In the vet’s office there is little to no discussion of the most important question, which is: is neutering good for dogs?

This does our dogs a serious disservice, with lifelong consequences for their health and wellbeing. 

Don’t take my word for it. I am not a vet. I am just a dog owner like you, trying to do the absolute best thing by her dog. This article is a collection of all the available information I could find on neutering. Click on the links within this article and read the studies yourself, make up your own mind.

If you do one thing before you neuter your dog, make sure you watch the Dr Karen Becker video below.

The great misconception

Most owners mistakenly believe that dog neutering is better for their pup’s health. Certainly in the past that was the prevailing advice. Particularly for female dogs.

But knowledge has advanced. A growing body of evidence now suggests the opposite. 

Before we examine the latest information, let’s take a step back. 

Why neuter a dog?

Neutering dogs is the norm in countries like the United States and Australia for one overriding reason: population control.

Avoiding unwanted litters and preventing the euthanasia of abandoned dogs in shelters is a worthy goal. However that’s not the whole picture. As a routine procedure, neutering provides a regular income stream for vets. In other words, powerful forces (other than an individual dog’s best interests) underpin the practice of desexing. Some of the motivation is welfare-based. But other drivers are purely economic.

In Europe — take Sweden, for example — owners rarely desex their dogs. 

The interwebs are brimming with conflicting information — and plain misinformation — about neutering, including from veterinary sources.

It’s no wonder owners are in the dark.

Here are some things to consider.

Dog neutering pros and cons 

Does neutering prevent or cause disease?

As recently as 2010 researchers still thought spaying was healthier for female dogs. Ideally, before their first heat, which meant at about six months. Some vets still impress on owners what they see as dog neutering benefits, without making owners aware of the downsides.

Dog neutering female dogs 

Mammary cancer

The disease vets cite as the reason to neuter females is mammary cancer. For decades they have been telling owners that spaying before the first heat dramatically reduces or eliminates the incidence of mammary tumors in dogs.  

Progressive vet Dr Karen Becker, dubbed “the most followed vet in the world”, says this is based on theory, rather than any actual scientific evidence.


This is a uterine disease that can be life threatening if left untreated. It can happen at any age but most often occurs in intact female dogs older than six years that have never been pregnant.

It’s one disease that can be prevented by spaying. And spaying is recommended for dogs with pyometra, to prevent recurrence.

Dog neutering male 

For male dogs, you’d have to say desexing decreases the risk of testicular cancer. But that’s like saying cutting off a woman’s breasts reduces her risk of breast cancer.

And neutering increases the risk of a staggering array of other diseases. 

Which diseases are increased by neutering? 

According to research, diseases made more likely by neutering include:

  • osteosarcoma in dogs (this is a bone tumor most often seen in large breed dogs)
  • acute pancreatitis
  • hypothyroidism (possibly)
  • obesity in dogs
  • splenic hemangiosarcoma
  • cardiac hemangiosarcoma
  • transitional cell carcinoma
  • hip dysplasia in dogs
  • cranial cruciate ligament rupture (CCL in dogs )
  • behavior problems including noise phobias, fear behaviors, aggression and undesirable sexual behaviors (see Dr Karen Becker)
  • endocrine disorders like Cushing’s disease (again Dr Becker explains this well)

There is a common belief that neutering a male dog prevents prostate cancer.

However, a small study at the Michigan State University’s College of Veterinary Medicine cast doubt even on that claim. The research suggests neutering, no matter at what age, has no effect on the development of prostate cancer.

These days the weight of evidence falls heavily in favor of not desexing. At least, not on health grounds.

More and more studies show neutering can increase the risk of multiple serious diseases later in life, from cancers to joint problems. It also makes behavior problems more likely, despite widespread beliefs to the contrary.

This is the case for both male and female dogs. 

Does age for dog neutering make a difference? 

Short answer? Yes. Research suggests neutering is especially detrimental for large breed dogs desexed at a young age.

Do any vets support keeping dogs intact? 

Dr Karen Becker says:

“When dealing with 100 per cent responsible pet owners, my preference is to leave dogs intact wherever possible”. 

Dr Becker says she changed her view on neutering after many dogs she spayed and neutered suffered irreversible metabolic diseases. The illnesses surfaced within a few years of the operation and left her with a profound sense of guilt, because she’d thought she’d been doing the right thing by the dogs in her care.

This video of Dr Becker’s is must watch viewing if you’re considering neutering your dog, especially if you’re under the impression that neutering is better for your dog’s health.

Are there any breed-specific studies about desexing dogs? 

In recent years a series of breed-specific studies have found:

  • Female rottweilers that kept their ovaries for at least six years were four times more likely to live long lives than early neutered rottweilers.
  • Golden retrievers desexed both before and after 1yo have much higher rates of joint disease like hip dysplasia and cancers including mast cell tumors in dogs, hemangiosarcoma and lymphosarcoma. When to neuter a golden retriever? Never. 
  • A german shepherd neutered before 1 yo triples its risk of joint disorders especially cranial cruciate ligament tears.
  • A 2014 study of vizslas found desexed dogs developed significantly more cancer of all types and more behavioral problems like fear of storms.

Dog neutering surgery means anesthetic

There’s also the fact that neutering is an anesthetic procedure. Vets can tend to be a bit blasé about operations — they do them every day — but any operation, and any anesthetic, puts stress on a dog’s system and carries risks. There can be serious side effects of anesthesia in dogs.  It’s worth considering whether you want to expose your dog to those risks for the sake of an elective procedure.

The risks of surgery can be particular to the breed. 

Acepromazine for dogs side effects

Vets commonly use this tranquilizer as a pre-anesthetic agent. 

It is 100% unsuitable for certain breeds. 

Boxers, for instance, are known to have a sensitivity to acepromazine.  It can cause a potentially serious heart arrhythmia. It also induces severe low blood pressure in many boxers. For these reasons the American Boxer Club recommends avoiding this drug entirely.

Once upon a time Plumb’s Veterinary Drug Handbook included a warning about acepromazine. It related not only to boxers but also greyhounds and giant breeds. However, the warning was removed from subsequent editions so your vet mightn’t be aware of it. 

If your dog is undergoing any anesthetic procedure, ask what drugs will be used and do your own research. Insist the surgeon avoids drugs known to cause problems, especially if your dog belongs to a breed with a known sensitivity. 

When can you neuter a dog? Will neutering a dog stop aggression?

One of the reasons given for dog neutering is that it supposedly makes male dogs less aggressive and that it decreases dog roaming and dog marking behavior  

Let’s set aside for a second the highly questionable practice of using surgery to achieve behavior modification. Even if that were ethical or advisable, the most up-to-date evidence suggests that neutering, particularly early neutering, actually increases the incidence of behavioral problems.

An article called ‘Five myths commonly associated with neutering in dogs’ published in the British professional website The Veterinary Nurse in 2014. It makes the point that “neutering is very unlikely to make dogs calmer”. 

The 2010 literature review I mentioned earlier even found neutering was possibly, though not definitively, associated with an increase in female dog aggression.

If you’re having behavioral problems with your dog, there are many ways to address it other than surgery. 

Preventing unwanted litters arising when an intact female dog lives in the same household as an entire male requires careful monitoring for when the female dog is in heat and separation for about a week. But estrus in dogs only happens about twice a year. 

Alternate dog neutering procedure: dog sterilization

Shelters often make dog spay or neuter a condition of adoption. Sometimes they desex puppies as young as six to eight weeks. 

Move heaven and earth to delay the procedure until the dog is as old as possible. 

Then, find a vet who is happy to sterilize (a de-sexing procedure that spares the testes/ovaries) instead of neuter. With the sex organs retained, the body can still receive the hormones they produce.  

Dr Karen Becker recommends sterilization over neutering of dogs and says an ovary sparing spay is just as effective as the standard procedure but “less invasive and eliminates the risk of endocrine damage”.

Dog neutering effects: Spay incontinence

Quite a large number of owners report a female dog leaking urine after being spayed. It’s another risk commonly associated with removing the hormone-producing ovaries. Spay incontinence symptoms can start a few years after the neutering procedure, often when the dog is still young. 

An observation about intact male dogs

One thing I have noticed is that other dogs (males) often respond aggressively to my unneutered dog for no apparent reason. He is a friendly, gentle pup. 

Dogs with intact sex organs smell different to neutered ones. Most domestic dogs living in cities where the norm is to neuter have not encountered many intact dogs. It adds an element on unpredictability and threat. Something to be aware of in order to take steps to protect your intact dog. If you’re wedded to partaking in off leash dog parks, that might be more dangerous than usual for an intact dog.  

More reading

Mucus in dog’s poop: When it’s a good sign

Are you speaking your dog’s language?

Raw meat dogs can eat

1 thought on “Neutering: Why The Old Advice Is Wrong”

    I agree totally and for years been telling people to research before proceeding with desexing – Its a big decision and requires researching. Too bad many folks believe the myth that they aren’t being responsible if they don’t neuter. For me they just are ignorant if they do!!
    i sent this article to a dozen people today !! thanks for posting it in simple terms so that those owners who don’t like to read can get through this article with some understanding of what they are considering. Dr Becker is a great vet – I have sent out her video for years too.


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