When to Spay or Neuter Your Dog?

When should I desex my dog

If you’re researching the best time to spay or neuter your puppy, you’ve probably noticed something frustrating, the advice is all over the place. Your vet might recommend six months. Your breeder says wait until two years. Your neighbour’s trainer has a completely different opinion. And then there’s that Facebook group insisting desexing will solve all your dog’s behaviour problems, or ruin them forever.

So what’s actually true?

Dog skeletal diagram showing growth plate closure timeline from 4 to 17 months

The Growth Plate Question

One of the biggest concerns people have is whether early desexing affects physical development, and it’s a valid one!

Growth plates are areas of developing cartilage tissue near the ends of long bones. They close at different times depending on the bone, the breed, and the individual dog. In general, small breeds finish growing earlier (around 9–12 months), while large and giant breeds can continue growing until 18–24 months or even longer.

Sex hormones, particularly oestrogen and testosterone, play a role in signalling growth plates to close. When you remove those hormones early, growth plates stay open longer, which can result in dogs growing slightly taller than they otherwise would have. This change in bone length can alter joint angles and load distribution, potentially increasing the risk of certain orthopaedic issues like cranial cruciate ligament disease or hip dysplasia, particularly in larger breeds, however, certain genetic factors that contribute to this should also be considered.

Recent research has also highlighted breed-specific differences. For example, studies from UC Davis on Golden Retrievers and Labrador Retrievers have shown higher rates of joint disorders and some cancers in dogs desexed before one year of age. Additional research examining 35 breeds found significant breed-specific differences in vulnerability to early desexing.

However, similar patterns haven’t been seen across all breeds, and smaller breeds appear to be less affected overall.

If you have a large or giant breed dog, or a breed predisposed to joint problems, waiting until your dog is fully grown (12–24 months depending on the breed) is worth discussing with your vet. For small to medium breeds with no known joint concerns, the timing may be less critical from a growth perspective.

What Desexing Does (and Doesn’t) Do for Behaviour

This is where things get murky, and where a lot of myths need clearing up…

Desexing removes the reproductive organs, which means it removes the primary source of sex hormones, testosterone in males, and oestrogen and progesterone in females. These hormones influence certain behaviours, but they don’t control everything your dog does.

Behaviours that ARE hormonally influenced…

  • Roaming or escaping to find mates: Desexing typically reduces or eliminates this.
  • Mounting or humping related to mating drive: Often decreases, though not always immediately, and not in all dogs.
  • Urine marking in intact males: May reduce in frequency, though some marking is also territorial or habitual and won’t change.
  • Inter-male aggression or competition: Particularly when triggered by pheromones from females in heat or competition with other intact males over mating opportunities.

However, if the aggression stems from fear, anxiety, frustration, environment guarding, or learned responses from past experiences, desexing won’t change it and behavioural work will be needed.

Behaviours that are NOT primarily hormonal…

  • Fear, anxiety, or reactivity: These are not caused by sex hormones. Desexing won’t reduce fear-based barking, lunging, or general nervousness.
  • Adolescent “difficult” behaviour: Not responding to cues, being easily distracted, this is normal brain development, not a hormone problem.
  • Overexcitement or hyperactivity: Not hormonally driven. This can be about about genetics, arousal regulation, impulse management, environmental context and consistency of training and management.
  • General day to day response to cues or recall issues : Training and environmental management are the main focus areas for this.
Female dog during reproduction cycle illustrating hormonal changes

Resource guarding or aggression over food, toys, or space: This is dependant… if a bitch is pregnant, having a pseudopregnancy/false pregnancy or in heat, then yes, that would be a hormonal influence.

However, context and background information is very important for this behaviour challenge and can be from panic responses of valuable items being taken away, learned or genetic behavioural traits.

The adolescent brain and behavioural changes

Adolescence in dogs (roughly 6–18 months, depending on breed) is a time of significant neurological and hormonal change. During this period, you might notice a couple of changes like…

  • Increased fearfulness or new fear responses (normal fear periods).
  • More impulsive or distractible behaviour.
  • Easily distracted and inconsistency with known cues.
  • Heightened reactive responses to the individual dog’s triggers.

These changes happen because of fluctuations in cortisol, serotonin, dopamine, testosterone (in males), and oestrogen, progesterone, and oxytocin (in females). This is a normal part of brain maturation.

The prefrontal cortex (the part of the brain responsible for impulse control and decision-making) is still developing during this time.

Desexing during adolescence won’t bypass these developmental stages. If your dog is suddenly scared of things they used to be fine with or seems to have “forgotten” all their training, that’s adolescence, not hormonal influences necessarily.

Training, understanding, a lot of patience, and consistent environmental management are what will help, not surgery.

So When Should You Desex?

spay and neuter timing

There’s no universal right answer, but here’s a framework to help you…

Consider waiting until at least 12 months (or longer for large/giant breeds) if:

  • If your dog is going through a fear period during adolescence or is generally quite nervous. The experience of surgery, anaesthesia, post-operative pain, and restricted activity can be stressful for certain dogs.

Going through this procedure when your dog is already more vulnerable to developing negative associations may intensify existing fears or create new ones related to handling, veterinary visits, or recovery restrictions.

If this is the case, a qualified behaviourist or force-free trainer can help you with a cooperative care program to build your dog’s confidence and create positive associations with the veterinary clinic before the procedure.

  • Your dog is a large or giant breed.
  • Your dog has a breed predisposition to joint issues (e.g., hip dysplasia, cruciate disease).
  • You want to allow full skeletal maturity before altering hormone levels.
  • Your dog is showing normal adolescent behaviour (not hormonally driven issues).

Desexing earlier (around 6–9 months) may be appropriate if…

  • Your dog is a small to medium breed with no known orthopaedic concerns.
  • There are significant challenges managing an intact dog in your household (e.g., other intact dogs, high risk of accidental mating).
  • There are health concerns your vet has identified (e.g., cryptorchidism, reproductive disease risk).

Waiting longer than 12–18 months might make sense if:

  • Your dog is still growing (check with your vet about growth plate closure).
  • You’re working with a veterinary behaviourist or qualified behaviour consultant on a treatment plan, and they’ve advised waiting.
  • You’re considering alternatives like vasectomy (for males) or ovary-sparing spay, which preserve some hormonal function while preventing reproduction.
When Should I Desex My Puppy - Common Questions

What About Those Difficult Behaviours?

If your dog is displaying challenging behaviours, reactivity, fear, aggression, hyperactivity, or anything else, then desexing should not be your first (or only) strategy.

Start with:

  • A qualified behaviour consultant or veterinary behaviourist who can assess what’s actually driving the behaviour.
  • A veterinary check to rule out pain or medical issues.
  • Management strategies to prevent rehearsal of unwanted behaviours.
  • A solid training and behaviour modification plan that addresses the root cause, not just the symptoms.

If the behaviour is hormonally influenced (like roaming, mounting, or inter-male aggression), desexing may be part of the solution, but it’s rarely the whole solution, and it won’t work overnight. Hormones can take weeks to months to fully leave the system, and learned behaviours often persist even after the hormonal influence is gone.

desexing timing options for smaller dogs

Last thoughts…

Desexing is an important decision, but it’s not an emergency. You have time to weigh up the options, talk to your vet, and consider your individual dog’s needs.

 

What we know from current research is that there’s no one-size-fits-all answer. Breed, size, health history, behaviour, and your home environment all matter. The old “six months for everyone” rule doesn’t reflect what we’ve learned in recent years about growth, development, and long-term health.

If you’re feeling conflicted, that’s completely understandable, because the science is genuinely complex, and the right choice for one dog might not be right for another.

Talk to your vet. Ask questions. And remember whether you desex at six months, 12 months, or later, the most important things you can do for your dog’s behaviour are provide good environmental management which includes prevention and positive reinforcement training, safe and gentle exposure during the socialisation period of development, and a stable, supportive environment. Those things matter far more than timing of desexing ever will.

References and Further Reading

Hart, B.L., Hart, L.A., Thigpen, A.P., & Willits, N.H. (2020). Assisting Decision-Making on Age of Neutering for Mixed Breed Dogs of Five Weight Categories: Associated Joint Disorders and Cancers. Frontiers in Veterinary Science, 7, 472.

Hart, B.L., Hart, L.A., Thigpen, A.P., & Willits, N.H. (2016). Long-Term Health Effects of Neutering Dogs: Comparison of Labrador Retrievers with Golden Retrievers. PLOS ONE, 11(2), e0150042.

Spain, C.V., Scarlett, J.M., & Houpt, K.A. (2004). Long-term risks and benefits of early-age gonadectomy in dogs. Journal of the American Veterinary Medical Association, 224(3), 380-387.

Salmeri, K.R., Bloomberg, M.S., Scruggs, S.L., & Shille, V. (1991). Gonadectomy in immature dogs: effects on skeletal, physical, and behavioural development. Journal of the American Veterinary Medical Association, 198(7), 1193-1203.

Mills, D.S., Braem Dube, M., & Zulch, H. (2014). Stress and Pheromonatherapy in Small Animal Clinical Behaviour. Wiley-Blackwell.

Overall, K.L. (2013). Manual of Clinical Behavioural Medicine for Dogs and Cats. Elsevier Health Sciences.

AVMA (American Veterinary Medical Association) – Gonadectomy Resources

https://www.avma.org/resources-tools/animal-health-and-welfare/elective-spaying-and-neutering-pets

Note: This blog is intended for educational purposes and reflects current veterinary and behavioural science understanding. Individual dogs vary, and decisions about desexing timing should always be made in consultation with your veterinarian and, where appropriate, a qualified behaviour professional

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