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  4. Benefits and risks of neutering pets – what is the evidence
Evidence collection27 November 2020

Benefits and risks of neutering pets – what is the evidence

Evidence-based veterinary medicineSmall animalsMedicine

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Published 26 November 2020 | Updated 30 October 2025

Introduction

Neutering is seen as a routine procedure for domestic pets in many countries and is promoted as part of responsible pet ownership and the primary means of population control. However, there is significant variation between countries, with some actively promoting neutering, for example through reduced licence fees for neutered dogs, while others, notably those in Northern Europe, consider the procedure of removing body parts during neutering to be a mutilation unless carried out for the treatment of disease.

Historically, the routine neutering of pets was justified as having health benefits for the individual animal alongside the benefits to the owner in terms of reducing unwanted behaviour, as well as benefits to society in terms of reducing unintended breeding and stray animals.

However, as veterinary knowledge has increased, it has become clear that neutering may carry risks as well as benefits for the individual animal and is not a panacea for all behaviour problems. This has led veterinary associations such as the BSAVA and AVMA to make statements to the effect that decisions regarding the elective neutering of pets should be made on a case by case basis. The evidence of risks and benefits of neutering should be weighed, considering the most appropriate timing and methods based on available evidence and discussion with the owner.

The purpose of this collection is to provide you with easy access to some of the available evidence, focusing on some of the most frequent areas of concern. This is not intended to be a comprehensive review of the literature, but rather a selection of references to inform your discussions with owners and guide your decision making regarding the elective neutering of pets.

New evidence is being published all the time, so you may wish to search for and critically appraise papers to answer a specific question about neutering. If so, RCVS Knowledge has developed an EBVM Toolkit to help you.

General

These papers provide an overview of the main discussion points around elective neutering of dogs and cats:

Attitudes to neutering

These papers report on research into the opinions of pet owners and veterinary professionals regarding neutering of dogs and cats:

Age at neutering

In recent years there has been a move towards routine neutering at a younger age. However, this move has generated concerns and a significant number of publications to discuss the optimum age for neutering. Links to a selection of these are provided below:

Paediatric neutering of cats

In cats the primary driver for early age neutering is to prevent unwanted pregnancy. However early age neutering has also raised concerns about the safety of the procedure in very young animals, the most appropriate techniques to use and the nursing care that will be required.

Factors affecting decision making for age of neutering in dogs

In dogs, decisions about the optimum time for neutering are complicated by the range of different sizes and breeds and the variation in disease risk for some conditions which may be affected by neuter status. The following papers give some general guidance regarding the optimum age for neutering but for details of the risks associated with specific conditions please see the section on the effect of neutering on disease risk.

Behaviour

While neutering can be helpful in the management of some problem behaviours, such as urine marking in the house, mounting and roaming, the effect of neutering on other behaviours is less easy to predict and careful assessment of the problem and discussion with the owners of the risks and benefits should be carried out. In cases of uncertainty it may be appropriate to consider temporary (non-surgical) hormonal control to assess the effect on behaviour.

Obesity

Concerns are often raised that neutering increases the risk of overweight and obesity and about the effect that this may have on health. However, in most cases any tendency towards increased bodyweight can be managed through appropriate nutrition.

Effect of neutering on disease risk

While the effect of neutering on the risk of certain disease conditions has been known for a long time, particularly in terms of reducing disease directly associated with the reproductive tract, recent published evidence has provided more detailed evidence regarding the size of the effect and shown that the removal of reproductive hormones can have wide ranging effects on the body.

While research papers normally report on the risks (positive and negative) of neutering in relation to a particular disease, it is important to consider the overall effect on the animal in terms of overall lifespan, which combine the risks from multiple causes. It is also important to be aware of confounding factors, such as age.

Longevity

Mammary tumours

The beneficial effect of timing of spaying on the incidence of mammary tumours has been widely taught and accepted. However, for a long time this advice appears to have been based on evidence from a single paper published in 1969. A systematic review published in 2012 concluded that “Due to the limited evidence available and the risk of bias in the published results, the evidence that neutering reduces the risk of mammary neoplasia, and the evidence that age at neutering has an effect, are judged to be weak and are not a sound basis for firm recommendations.”

As well as questions about the benefit of neutering on preventing mammary tumours, questions also arise about whether ovariohysterectomy at the time of mammary tumour removal is beneficial.

Pyometra

Surgical ovariohysterectomy is considered the safest and most effective treatment, as the source of infection is removed, and recurrence prevented. Medical treatment can be an alternative in young and otherwise healthy breeding animals with open cervix and without other uterine or ovarian pathologies.

Medical treatment of pyometra

Urinary incontinence

In the case of urinary incontinence there is published evidence looking, not only at the risk of urinary incontinence associated with neutering, but also at the effect of age of neutering on the risk.

Prostatic disease

While experimental studies have demonstrated the effect of testosterone (and therefore the protective effect of castration) on the development of benign prostatic hyperplasia more recent epidemiological studies have demonstrated an increased incidence of prostatic carcinoma in castrated dogs. It may therefore be necessary to weigh the relative risks of different prostatic diseases in making recommendations for an individual dog.

Other

Breed specific disease risk

Alongside evidence relating to the effect of neutering on disease risk there are now a number of published studies looking at disease risk in certain breeds. There have been a number of papers on Golden retrievers in the US, but studies of other breeds have also been published. While this information can be useful when assessing the risks and benefits of neutering to an individual it is important to appraise the evidence presented to assess whether it is applicable to your patient. This can be particularly important with cohort studies which may be reporting on the disease risk in a group of animals which may not be representative of the whole population. For further guidance on appraising cohort studies please refer to the cohort study checklist in the EBVM toolkit.

Golden Retrievers

The Golden Retriever has been the subject of a number of studies relating to the effects of neutering on different disease conditions. This is not to say that the risks of neutering are greater in this breed, just that they appear to have been the first breed subject to this research.

Surgical options

Once the decision to neuter has been made there are still decisions to be taken regarding the most appropriate technique.

When deciding on a surgical technique, it is also important to consider the possible risks and complications, as these can have a significant effect on animal welfare, client satisfaction and the wellbeing of veterinary staff.

Alongside primary published evidence there are also a number of evidence reviews available relating different surgical options:

As well as looking at complication rates in the published literature it may be helpful to carry out a clinical audit of complications following routine neutering in your own practice. You can benchmark your own practice by contributing to the National Audit for Small Animal Neutering https://vetaudit.rcvsk.org/nasan/

Non-surgical control of reproduction

Rabbits and other small animals

About evidence collections

Evidence collections bring together collections of published papers on topics of interest and importance to the veterinary professions. Papers are chosen for relevance and accessibility, with the full text of articles either being available through the RCVS Knowledge library, on open access or from other publications to which a significant number of veterinary professionals are likely to have access. This means that there may be relevant evidence that is not included.

If you would like assistance in searching for further evidence on this topic you may find the following helpful EBVM Toolkit 2: Finding the best available evidence.

If you would like to suggest a paper for inclusion in one of our published evidence collections, or a topic for a future collection, please email library@rcvsknowledge.org

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