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Dog Neutering: A Guide to Benefits, Risks and When to Neuter

Understanding Neutering

At Animal Trust, we believe that neutering your dog is usually the responsible decision to help safeguard your dog's health and well-being. By neutering your pet early, you can prevent unwanted pregnancies and give them benefits like a significantly lower risk of mammary tumours in female dogs, avoid serious health issues like pyometra later in their lives and prevent false pregnancies.

And you're not only helping your pet live a healthier life but also contributing to the well-being of other animals and reducing the number of unwanted pets in the community. However, the decision isn’t quite one-size-fits-all, and in this article we discuss some of the factors that may affect when to neuter your dog, or indeed whether in some cases neutering isn’t the right decision for them.

Dog Neutering: A Guide to Benefits, Risks and When to Neuter

Male Dogs: Advantages and Disadvantages of Neutering

Male Dogs: Advantages and Disadvantages of Neutering

Males with undescended testicles should always be neutered as a high proportion will develop testicular cancer otherwise. For other dogs there are a mix of benefits and disadvantages with neutering.

  • Eliminates the risk of testicular cancer

  • Greatly reduces the risk of prostate disease

  • Can have a beneficial effect on some problem behaviours such as aggression, roaming and urine marking

  • Reduces frustration, some dogs may go off their food if there is a female in heat nearby and may be more likely to roam

  • Controls or eliminates growth of perianal adenomas

  • Prevents perineal hernia formation

  • May exacerbate fear/anxiety-based aggression

  • Neutered dogs burn fewer calories at rest, so they are more prone to weight gain, this can be managed by a healthy diet and exercise

  • Neutering of older dogs may cause changes in temperament, so it is generally advised to be done earlier rather than later

  • There appears to be a slightly increased risk of hypothyroidism in neutered animals

Female Dogs: Advantages and Disadvantages of Neutering

Female Dogs: Advantages and Disadvantages of Neutering

For female dogs, spaying is usually best done 2-3 months post-season, when hormone levels are at their lowest. It is important that they are not spayed during their season, as the risk of complications is much higher.

  • Prevents unwanted pregnancy

  • Greatly reduces risk of mammary tumours, especially if spayed before the first season

  • Eliminates risk of pyometra (affects up to 25% of unneutered female dogs and can be fatal)

  • Prevents false pregnancies, which are a natural reaction to hormones in females; however, some individuals can be very subdued, go off their food and they may even become unwell

  • May reduce aggression between females in a household

  • Prevents unwanted attention from male dogs

  • May help with the management of some diseases such as epilepsy and diabetes

  • Occasionally may cause changes in hair coat quality; however, this is purely cosmetic

  • Neutered animals burn fewer calories at rest, so are more prone to weight gain, this can be managed by a healthy diet and exercise

  • Neutered females are slightly more prone to urinary incontinence as they age. This risk is increased in large breeds, especially if neutered early. USMI affects approximately 3% of bitches in the UK. This is thought to be due to a combination of decreased hormones and sometimes weight gain. It is well managed with medication in most cases.

Neutering My Dog - Frequently Asked Questions

For some large breeds (20kg +) like Golden Retrievers, Labradors, and German Shepherds, it is sometimes advised to wait until skeletal maturity before neutering, as some studies have shown that early neutering in these breeds may increase the risk of joint disorders and some other conditions later in life. Therefore, 18 months old can be a sensible time for neutering, but it can be done earlier if it is necessary for other reasons.

In contrast, small breeds generally, small breeds do not show the increased risk of joint disorders and can therefore be neutered at a younger age.

The vast majority of dogs will not have any adverse effects, however, a 2019 study found that some large breeds such as Irish Setters, Dobermans, Weimaraners, Hungarian Vizslas, and Dalmatians have a higher risk of early-onset urinary incontinence post-neutering. This is particularly so for female dogs and if neutered before 6 months. Therefore, delayed neutering until a later age is sometimes done in these breeds.

Dogs with anxiety, nervousness, or fear aggression may benefit from being neutered after maturity (12-24 months), or in some cases it may be decided not to neuter at all; however, some dogs with behavioural issues will benefit from neutering, as testosterone can increase aggressive behaviour, primarily between male dogs. A hormonal implant, which lowers testosterone levels, may be used before surgical castration to assess potential behavioural changes, as unlike surgery, the implant's effect is reversible.

It’s important to remember that testosterone is not involved in most disobedient behaviours, and hard-wired behaviours like humping and mounting may persist in neutered animals as learned behaviours.

Author

Written by Dr. Mariella Roberts, Veterinary Surgeon, Animal Trust Vets CIC | Published February 2025 | Review date February 2028 | This advice is for UK pets only

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