What Is The Best Age To Desex A Dog?

I’m going to lead you through the evidence we have for the age to desex a dog. I’m not going to give you the ‘right’ answer, but instead the tools so you can make the best decision for your dog. With the new mandatory 6-month desexing in Adelaide, this is the evidence you may need to ask your vet for a postponement.

Beware simple answers. The real world is frustratingly not in black and white; anyone who claims otherwise is either misleading themselves or others. The job of science is to get as close to the truth as is humanly possible.

Firstly, let’s establish the reasons why we desex male and female dogs. Here’s the evidence we have in favour of neutering.

Why Desex Male Dogs

  • Lifespan is increased
  • Aggression between dogs and aggression towards family members are reduced (read here for a full discussion of the effects of desexing on aggression)
  • Urine marking and roaming are reduced
  • Medical conditions such as prostatic enlargement, cystine bladder stones, perineal hernia, testicular tumour & perianal tumour are reduced or eliminated.

Why Desex Female Dogs

  • Lifespan is significantly increased
  • Heat periods and unwanted pregnancy are eliminated
  • Pyometra (uterine infection) is prevented

To help dog owners I tell them:

Desex males for behaviour; Desex females for health. References can be found below.

Why NOT Desex A Dog?

Apart from infertility, proven negatives associated with desexing include:

Although they sound scary, we shouldn’t be concerned about the cancers associated with desexing. That’s because there’s a trump card: neutering gives a moderate increase in lifespan to both sexes of 9 to 12 months. In other words, although some causes of death become more common, other causes of death must become less common.

I’m much more concerned about accidentally increasing the rate of debilitating non-life-threatening diseases. That’s the information I use to decide when to desex.

When To Desex Dogs

There are four times advised by different groups:

  1. Early age desexing as advocated by rescue shelters and some breeders
  2. 6-month desexing as advocated by most vets
  3. Late age desexing, typically over 12 months of age
  4. or Not at all, which from 2018 is no longer an easy option in SA

In Australia, there is a strong push from society for all dogs to be desexed. I think an impartial reading of the pros and cons of desexing male dogs will lead most people to decide it’s also in their pet’s best interests. Female dogs, who get a comparatively greater lifespan advantage, present an even more compelling case. Although you are welcome to disagree, to me the only decision is when to do it.

Now have a look at this chart, in which I’ve summarised the results of three large studies from the University of California-Davis. Feel free to focus on the details but I’ll explain the main points later. These are the only big studies that compare outcomes at different desexing ages.

desex neuter problems
Age of Desexing vs Risk of Cruciate or Hip Problems

The Problem With The Evidence

Striking isn’t it? It’s clear that early desexing increases the risk of joint diseases in susceptible dogs. The theory is that hormones influence normal development of joints in some breeds. Once a joint is fully grown, hormones shouldn’t make much of a difference. But there’s still a small problem: body weight.

Not one of these observational studies is controlled for weight. They have simply taken data from a large clinic’s files without attempting to compare dogs of the same body condition score. The desexed groups are almost certainly heavier, and we know that weight is a significant risk factor for cranial cruciate ligament disease (CCLD) and hip dysplasia (HD). This is a quote from one study:

…the occurrence of HD and CCL in early-neutered dogs is a combined function of the effect of neutering on growth plates, as well as the increase in weight on the joints brought on by neutering. Reference 1

This doesn’t change the findings, which are statistically significant for most of the large differences. However, the question remains: if an owner can control their desexed dog’s weight, is there still a risk of joint problems? Only a future study comparing puppies of the same weight will answer that question. Until then (if ever!), it’s safest to follow these guidelines…

The Best Age To Desex A Dog

New recommendations to dog owners are:

  •  6 month desexing is still likely to be the best time for most dog breeds. This avoids a heat period in females and pre-empts most behaviour change in males.
  • Late desexing over 12 months is recommended for breeds prone to hip dysplasia and cruciate disease. It may also be helpful for anxious males and leaky females.
  • Early age desexing is important for rescue shelters to avoid overpopulation. There have been very few good studies looking at 8 week desexing but in my opinion it’s likely that any effects on joints will be magnified by taking desexing even earlier. Read here about the risks of incontinence associated with early age desexing.

For dog owners wanting to preserve female hormones through life, Ovary Sparing Spay is another alternative. Follow the link to learn more.

Many owners of male dogs who opt for late desexing find problem behaviours develop that can be quite hard to manage. To these owners, we say: go as far as you can but don’t feel guilty to give up early. Bad habits can be very hard to stop once they start, and the evidence isn’t ironclad. Any delay should help.

When Desexing Exemptions Will Apply

From July 2018, with compulsory 6-month desexing in South Australia, vets will need to register an exemption of some dogs until maturity. The period can be up to 18 months. It will apply to any breed shown to be at higher risk of hip dysplasia or cruciate disease, not just the ones featured in these studies. This is speaking to the evidence in the safest way and it’s only right. It’s then up to owners if they want to exercise this option.

Up to now, there’s not enough evidence to extend this advice to other breeds but you can rely on us to keep you informed as new facts emerge.

Further Reading

References & more studies showing health effects of desexing can be found at our page on Desexing Male Dogs. The three studies quoted here are:

  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. Full Article.
  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. Full Article
  3. Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2016). Neutering of German Shepherd Dogs: associated joint disorders, cancers and urinary incontinence. Veterinary Medicine and Science. Full Article


By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These blogs are from a series regularly posted on Facebook and Twitter. Subscribe via email here to never miss a story!

Have something to add? Comments are welcome below and will appear within 24 hours of lodging.


16 Replies to “What Is The Best Age To Desex A Dog?”

  1. Hi Andrew,
    We have a nearly 1 year Male border collie not desexed yet ( the breeder suggested to wait untill he ll be 18 months) and soon we’ll have a second pup a husky cross kelpie female.
    To avoid issues between them we were thinking to have the new pup desexed pretty soon . She will be 10 weeks old when we ll get her . What’s your suggestion? Should we desexed both or just the female now and the Male when he ll be 18 months old?

    1. Hi Luca. There is no compelling reason to wait any longer to desex your male dog, and in fact there are distinct behavioural disadvantages (let’s not forget that dog breeders are much more willing to manage male dog behaviour and rarely have small children around). There are, however, compelling reasons to delay desexing your female (see this page on incontinence for example). Therefore, I would get the male done ASAP and leave the female to have one heat.

  2. I have a male border collie who zi would like to do agility with and wanting to know if getting him desexed at 6mths wont effect his bone growth.

  3. Hi Andrew
    Does sterilisation as opposed to desexing of a male dog satisfy the intent of South Australian legislation?
    Thank you

  4. Hi Andrew, I have just bought an 8 week old female Dalmatian. Is she classed as a large breed. Should I wait till she stops growing? I am contemplating a hysterectomy and leaving the ovaries.
    Thanks Marie

  5. Hi Andrew, I have just brought home a female Borzoi pup. The breeder has recommended a late desexing for her, as she is a giant breed and early desexing could disrupt her hormones causing excessive growth issues. As I want to do the best for her, I am interested in the veterinary point of view. Is this practise recommended?

    1. Hi Donna. This article sets out everything we know about the optimal desexing age. Therefore you are welcome to make up your own mind from the evidence! The short answer is: yes, we advise waiting until maturity in large breeds.

  6. We are looking to buy a labdradoodle later in the year. The problem is every breeder I have contacted across Australia , whether a member of the Australian Labradoodle association or not, only sells pups at 8 weeks that have already been desexed. As a GP and reading the evidence that concerns me. Are you aware of any Labradoodle breeders that either offer a contract to be desexed at 6 months or offer a tubal ligation instead ? We want our dog desexed just not at 6-7 weeks. Any advice appreciated.

    1. Hi Kylie- you raise a very good point. I do not know of any that do not desex early but I am almost certain they will exist. As for those that do it early, please add your voice to the evidence. It’s a strange culture this breed group have developed and it needs to change.

      1. Hi Andrew,
        My puppy was desexed when we bought her, but she appears to have come into ‘season’ at 7 months !-, is it ok to desex her whilst she’s now supposedly in ‘season’ ?

        1. Hi Gloria. It’s extremely rare for dogs to come into season after being spayed, and would make me wonder if she was spayed at all or if there’s something else wrong. If you haven’t already, please get a vet checkup. I always advise waiting until a season has finished before desexing.

  7. Hi my name is Nellie and I have a cross Maltese Lhsa Apso male dog. He is ten years old and in the last couple of months after he has an
    erection the foreskin does not cover his penis. I took him to the vet and they said he needs to be desexed or he is going to have all sorts of problems. I have always had the impression that it was dangerous to desex them at such a late age. Is it ok to do or not.

Leave a Reply to Andrew Cancel reply

Your email address will not be published. Required fields are marked *