When Should You Spay or Neuter Your Dog?

The research is confusing – here are some guidelines

31 October 2023

When you adopt a puppy you have a lot of choices to make, from choosing the best diet to finding the perfect training classes. One of the biggest decisions you’ll have to make is when to spay or neuter your puppy.

For decades it’s been common to spay or neuter dogs between the ages of four to six months, but recent research has suggested that may be too early for some puppies. While it’s hard to ignore the many health benefits of spaying and neutering, the question of when to schedule your puppy’s surgery is a little more complicated. Learn about when to spay a dog and when to neuter a dog based on their breed and size.

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Neuter vs spay: what is the difference?

First things first: you need to understand the difference between neutering and spaying. While these terms both refer to sterilisation, they’re not interchangeable.

Neutering a dog, a surgery known as castration or an orchiectomy, involves removing the testicles and associated structures from a male dog, eliminating the animal’s ability to reproduce. Spaying refers to the same concept for female dogs, known as an ovariohysterectomy. The dog spaying procedure involves removing the uterus and ovaries to end a female dog’s heat cycle and the possibility of pregnancy.

Both spaying and neutering prevent litters of puppies, reducing the animal population and the need for pet euthanasia in shelters.

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At what age should I spay or neuter my dog?

So, when is the best time to spay a dog? Many vets used to recommend spaying or neutering a puppy between four and six months of age, but more recent studies suggest that the right time for the surgery depends on the dog’s size and breed. If you’re determining when to spay a female dog it’s best to discuss in detail with your vet, who can help you identify any potential medical concerns in the future that could be impacted by an early spay.

Larger dogs often take longer to reach sexual maturity, so vets now suggest waiting to spay or neuter until these pups are a little older. While you should always discuss your dog’s specific needs with your vet, below are some general guidelines for when to neuter a dog or spay a dog based on size and sex:

For small dogs (5–10kg), females should be spayed at around five to six months old and males at around six months.
For medium-sized dogs (between 11–25kg), the same guidelines apply.
For large dogs (over 25kg) or giant dogs (over 40kg), males should be neutered after their growth ends, usually around nine to 15 months. For females, the decision should be based on additional factors, such as disease risk and your lifestyle, but you may want to wait to spay your dog until they’re at least nine months old.

Signs your female dog needs to be spayed

Most female dogs enter their first heat, known as oestrus, when they’re around nine or 10 months old. If you don’t spay your dog prior to her first heat, you can expect to deal with some less-than-fun new behaviours that serve as signs your dog needs to be spayed, such as:

Up to two weeks of bleeding, which means investing in and changing dog nappies.
Abrupt changes in mood.
Unwanted attention from male dogs in your area (which can mean stray dogs showing up at your door or in your garden).

If you choose to spay your dog before her first heat, you can avoid all these behaviours, as well as never worry about your dog ending up pregnant with a litter of pups you’ll have to care and find homes for.

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Signs your male dog needs to be neutered

For male dogs, their first heat leads to multiple new behaviours, which can range from the frustrating to the dangerous, such as:

urine marking, both outside and in the house
mounting and/or humping
an overprotective attitude
aggression
roaming and running away, which can result in injury or even death

Neutering your dog before their first heat can curb their instinct to wander and keep your dog safe at home, as well as prevent them from harassing local female dogs.

What about large-breed dogs?

Different dogs mature at different ages, and large dogs tend to reach sexual maturity much later than small and medium dogs. While it’s likely perfectly safe (and healthy) to spay or neuter toy and medium breeds as early as at 6–9 months, spaying or neutering large breeds too soon can lead to a number of health issues later in life, including urinary incontinence, orthopaedic issues and some types of cancer.

Keep in mind that delaying spay or neuter until your large dog is older does not guarantee your dog won’t suffer from any of these conditions. However, the benefits of waiting to neuter your dog include the reduced likelihood of some illnesses.

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What are the benefits of neutering or spaying my dog early?

The earlier you spay or neuter your dog, the easier the surgery for both the vet and the patient. Younger dogs recover more quickly from these surgeries, which also tend to be less complicated if performed before your dog reaches sexual maturity.

A quick recovery is not the only benefit of an early spay or neuter. If spayed early, your female dog will never go into heat, which means no dealing with a fertility cycle and no risk of pregnancy. Spaying your dog also eliminates the risk of any illness associated with the reproductive organs, like uterine or ovarian cancer.

The benefits of neutering a dog include preventing the urge to roam, keeping your pup away from dangers like traffic, fights with other animals, injury and theft. Neutered dogs will also not engage in that obnoxious humping behaviour that embarrasses pet parents in front of every houseguest.

Best of all, spaying and neutering can increase your dog’s life expectancy so you can keep your beloved friend around even longer.

What are the disadvantages of neutering or spaying my dog early?

Sex hormones are part of any animal’s natural development, and spaying or neutering eliminates some of those hormones, which can affect all parts of your pup’s development. If you spay or neuter too early, your dog’s psychological, cardiovascular and musculoskeletal development could be affected.

And as mentioned above, spaying or neutering a large dog too early can lead to increased risks of multiple health conditions, such as:

joint issues, such as hip and elbow dysplasia
cranial cruciate rupture or tear
some cancers, such as lymphoma

What are the benefits of waiting to spay or neuter your dog?

If you have a large- or giant-breed dog, waiting a little longer to spay or neuter can help reduce the risks of health issues, such as hip dysplasia, immune disease and some cancers, as well as prevent urinary incontinence and struggles with weight gain.

Will spaying or neutering change my dog’s behaviour?

Spaying or neutering can prevent quite a few unwanted behaviours, like urinating indoors and mounting. Neutered males also no longer have the innate desire to roam, which can help keep your dog safe. Many believe that one of the side effects of neutering a dog is reduced aggression but that hasn’t been definitively proven.

Are there any risks associated with spaying or neutering?

As with any surgery, there are some risks involved. Adult dogs or dogs with other health conditions are more likely to experience complications from surgery, and some pet parents have reported that their dogs gained weight after spaying or neutering because of the changes in hormones. Weight gain is an especially common side effect of spaying a female dog.

Surgery also involves the use of anaesthesia. This is just as safe for dogs as it is for humans but in rare cases can have a negative effect. However, spaying and neutering are the most common – and often safest – surgeries that veterinarians perform, so your pet will most likely recover with no issues.

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Are there alternatives to consider?

While spaying or neutering are the most common sterilisation options for dogs, there are some other alternatives your vet may bring up:

Vasectomy: while not common, there are procedures for male dogs similar to those for humans that sever the tubes which move sperm from the testes.
Partial spay: a hysterectomy for female dogs involves removing the uterus, but leaving the ovaries. Dogs who undergo this surgery will still go into heat but won’t bleed and are unable to become pregnant.
Ovariectomy: on the opposite spectrum, this surgery removes the ovaries but leaves the uterus, which eliminates the heat cycle entirely.
Nonsurgical sterilisation: while still in the early stages, researchers are working to develop an injection for male dogs that stops sperm production without requiring surgery.

Frequently asked questions

How long is the recovery period after spaying or neutering?

While it takes about 10–14 days for a dog to fully recover from spay or neuter surgery, most dogs will begin to feel better in just 24–48 hours.

How much does it cost to spay or neuter a dog?

The cost of spay or neuter surgery varies widely depending on your location, the size of your dog, the type of surgery and your pet’s age. A routine neuter can range anywhere from £100 to around £300, while a routine spay can be £150 to over £360.

Fortunately, many areas have local free or low-cost spay/neuter clinics, so contact your local council or the RSPCA to find out about opportunities near you. You may also choose to adopt a dog from a shelter that includes spay or neuter services in their adoption fee.

Is it better to spay before or after first heat?

Spaying before your pet enters their first heat decreases your dog’s risk of some cancers and reduces the hassle of cleaning up after a dog in heat, which can definitely get messy.

What are the cons of spaying too early?

For larger dogs, spaying too early can lead to health conditions like hip dysplasia, torn ligaments, urinary incontinence, and some cancers.

What happens if you neuter too early?

Neutering a dog too early can result in a loss of bone mass and even lead to behavioural issues, like aggression.

References

Dr. Alycia Washington, DVM, MS

Alycia Washington, DVM, is a small animal emergency veterinarian based in North Carolina. She works as a relief veterinarian and provides services to numerous emergency and specialty hospitals. Dr. Washington is also a children’s book author and freelance writer with a focus on veterinary medicine. She has a special fondness for turtles, honey bees, and penguins — none of which she treats. In her free time, Dr. Washington enjoys travel, good food, and good enough coffee.

When Should You Spay or Neuter Your Dog?

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Neuter vs spay: what is the difference?

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