Dog neutering – a guide to castration and spaying


  • ‘Neutering’ is the procedure to remove testicles from a male (castration), and ovaries from a female (spay).
  • Neutering prevents unwanted pregnancies, pregnancy related illness and has many other health benefits.
  • Most dogs can be neutered from 4-6 months old, but it’s important to speak to your vet about the right time to neuter your dog.
  • PDSA vets recommend that all dogs are neutered unless your vet advises against it.

What is neutering?


Neutering is a routine procedure that involves removing your dog’s sex organs to prevent unwanted pregnancies, pregnancy related illness, and conditions such as testicular, ovarian, and mammary cancers. The male procedure is called castration, and the female procedure is called spaying.

Why neuter?

Some of the benefits of neutering include:

The benefits of neutering a female dog include:

The benefits of neutering a male dog include:

  • Prevents testicular cancer
  • Reduces the chance of prostate problems such as Benign Prostatic Hyperplasia (BPH) later in life
  • Reduces the urge to seek out a female dog to mate with, and therefore reduces the urge to roam away from home
  • Reduces the chance of behaviours such as humping

When is the best time to have my dog neutered?

Most dogs can be neutered at around 6 months old, but it’s important to discuss the timing with your vet because it should always be based on the following:

  • Breed/size: If your dog is a large breed, your vet might recommend neutering them slightly later. You can find out more in our neutering FAQs.
  • Behaviour: Neutering can improve some unwanted behaviours, but occasionally it makes others, such as nervousness, a bit worse. For this reason, if you are considering neutering your dog for a behavioural reason, always talk to your vet and/or a qualified animal behaviourist beforehand.
  • Weight: Overweight/underweight dogs are more at risk of complications during surgery, so it’s best to get them into good shape before neutering.
  • Seasons (female dogs only): It’s safe to neuter your dog before her first season, but once she has had a season, you’ll need to wait for approximately 3 months – neutering sooner than this can cause ongoing hormonal problems.
  • Other health conditions: Certain health conditions may change your dog’s ideal neutering time – speak to your vet for more information.

What will happen when my dog is neutered?


  • Food – you will need to starve your dog for 6-8 hours before they go under anaesthetic, i.e. give them dinner the night before, but no breakfast or treats on the morning of their operation. This is to make sure their stomach is empty so they don’t regurgitate and choke under anaesthetic.
  • Water – you can leave water down for your dog until 2-3 hours before they go in for their operation, i.e. take it away at 6-7am the morning of their surgery.
  • Health – if your dog has been poorly in the days leading up to their operation, let your vet know so they can give them a check over and make sure they are fit for surgery.
  • Cleanliness – try to make sure your dog is clean when they go for their operation, and if they are very mucky give them a bath the night before.

The operation

  • Your vet will check your dog over, give them a light sedative and some pain relief, and settle them in a warm, comfortable kennel.
  • Once the sedative has taken effect, your dog will be put under a full/general anaesthetic.
  • They will then be carefully monitored, while their surgery site is clipped and cleaned ready for the procedure.
  • If your dog is female, your vet will make a small incision along the middle of her tummy so her ovaries and womb can be carefully removed.
  • If your dog is male, your vet will make a small incision just above the testicles so that both testicles can be carefully removed.
  • If your dog is cryptorchid (has one or two retained testicles), they are likely to need two incisions for their castration. For more information read our article ‘Cryptorchidism / undescended testicles in dogs’.


  • Your dog will wake up from their anaesthetic under the careful watch of a vet or vet nurse, then placed in a warm, comfortable kennel to recover.
  • Most dogs can return home a few hours after their operation, but if your dog takes a bit longer to come round from their anaesthetic, they may need to be monitored for longer.

Recovery, home care and check-ups


When your dog first comes home, they might be a bit sleepy and disorientated. This can last for several hours, but they will start to feel much more normal as the anaesthetic drugs leave their body (usually within 24-48 hours). Once your dog is feeling brighter and more energetic, it’s likely that they will want to run around as normal, but it’s important that they rest for 7-10 days to prevent any complications with the wound and internal stitches. If necessary, you may need to keep your dog on a lead, crate them, or confine them to one room. Once they have recovered from being neutered, you can start slowly returning them to exercise.

Protecting the wound

It’s likely that your dog will be given a protective cone/buster collar to stop them licking and nibbling at their wound. Speak to your vet beforehand if you would like a soft buster collar or a body suit for you dog.


Your dog will usually need a check-up 2-3 days and 7-10 days after their operation, to check they are healing well and feeling okay after their anaesthetic. However, if you have any concerns about your dog before their check-up, always call your vet for advice.

Stitch removal

You may be able to see stitches in your dog’s wound depending on whether your vet used dissolvable or non-dissolvable stitches. Dissolvable stitches can’t be seen and don’t need removing. Non-dissolvable stitches can be seen and tend to need removing 7-14 days after the operation.


Neutering is a relatively safe, routine procedure, performed by most vets on a daily basis. However, like any operation there are always risks and the potential for complications during and after the surgery. Your vet will discuss the risk with you beforehand – don’t hesitate to ask any questions if you have any concerns.

Dog neutering cost

The price of neutering your dog will depend on their size, gender, and your individual vet practice – call your vets for more information about prices. If you are struggling with the cost of neutering your dog, speak to your vet practice and local dog warden to find out if there is any charity help available.

Dog insurance covers a wide range of medical conditions and procedures, but excludes expenses related to preventive treatments such as vaccinations, worming, and neutering/spaying since they are considered inherent costs of pet ownership.

'Chemical' castration

Male dogs can be chemically castrated with an injection or implant that mimics the effects of castration. Chemical castration doesn’t require a general anaesthetic and the effects are reversible. Your vet might suggest chemical castration if they want to test how castration affects your dog before performing a permanent procedure.

Keeping unneutered dogs safe

If your dog is unneutered it’s important to know how to keep them safe.


If you have an unneutered female dog, you will need to keep her away from all unneutered male dogs when she is in season/on heat. After her season, you will need to monitor for signs of pyometra (womb infection) and false pregnancy. It’s also important to regularly check her mammary glands/breasts for lumps.

Male dogs

If you have an unneutered male dog, you will need to keep him away from any unneutered females while they are in season, be careful around other entire male dogs (aggression is slightly more likely), and monitor for any penis or testicle problems, especially later in life.



Will neutering make my dog fat?

Due to the hormonal changes associated with neutering, your dog will need around 30% less calories once they have been spayed or castrated. We recommend that you reduce your dog’s portion sizes, or find a food specifically for neutered dogs, which is naturally lower in calories. If your dog is putting on weight after neutering, talk to your vet or vet nurse about the best ways to keep them in shape.

Will neutering change my dog’s personality?

If your pet is confident, happy and well socialised, then it’s very unlikely that neutering them will change their behaviour or personality.

However, if they are under-confident, fearful, or have behavioural problems, neutering could make them worse. This is because sex-hormones such as testosterone, tend to boost confidence, so a reduction in these hormones away at the wrong time might reduce your dog’s confidence, making them more fearful and/or aggressive.

If your dog is over-confident, or urine marks in the house, they might benefit from neutering, but the decision to neuter should always be thoroughly discussed with your vet and an ABTC accredited pet behaviourist if you are worried about their behaviour.

When is the best time to neuter a large/giant breed dog?

If your dog is a large or giant breed, your vet may advise waiting until they are a bit older before neutering them. This is because they are likely to take longer to reach their adult size, and their growth plates (which control bone growth), take a few months longer to close. There is some evidence to show that neutering large/giant breed dogs at 4-6 months can lead to joint problems in later life. Always speak to your vet about the best time to neuter your dog.

Does neutering help reduce aggression in dogs?

We now know that neutering doesn’t prevent aggression in dogs, and in some circumstances, can even make it worse. If your dog is showing signs of aggression, we advise speaking to your vet and an ABTC accredited pet behaviourist ASAP – getting help early is extremely important.

I am a PDSA client, how do I get my dog neutered?

We face a huge demand for our services at PDSA, and although our priority is urgent and lifesaving treatment, wherever possible we also provide preventive services such as neutering. To find out whether your local PDSA is offering neutering visit our eligibility checker. If your local PDSA is unable to offer neutering at present, we recommend that you try another local vet practice. Don’t worry, if you are registered with PDSA client and have your dog neutered elsewhere, you will stay registered with us should they become unwell at any point.

Does my dog need to have a litter before I spay her?

No, there is no evidence to show that having a litter of puppies is of any benefit to your dog. Pregnancy and giving birth can come with complications, and looking after a litter of puppies is hard work, expensive and time consuming – certainly not something to enter into without a great deal of thought and planning. If you are certain you want to breed from your dog, speak to your vet for advice beforehand.

Will neutering make my dog incontinent?

Spaying your dog when she is extremely young (less than 3 months old) can increase her risk of developing a type of incontinence called USMI, but once she is 3 months old, there is no evidence to show that it increases risk of incontinence later in life. Speak to your vet if you’re worried about the best age to neuter your dog.

Can a dog be speyed while in heat?

Ideally not. Spaying a dog in heat is much more risky because the blood vessels around the uterus become much bigger, and hormonal problems such as a long lasting false pregnancy can develop afterwards. For these reasons, it’s best to spay your dog 2-3 months after her season (unless there is a specific reason to do it sooner).

Why does my male dog still look like he still has testicles after his castration?

When a dog is castrated, the testicles (balls) are removed but the scrotum (ball sack) isn’t. This means sometimes they look like they still have testicles after their operation. Over time the scrotum will shrink and become less noticeable. If you notice swelling or redness in your dog’s scrotum after their surgery, contact your vet for advice. There are also two spherical glands called the ‘bulbus glandis’ that sit either side of the penis and swell when they become excited or aroused. These glands are often mistaken for testicles.

Will my dog need to wear a buster collar after being castrated/spayed?

Yes, most dogs need to wear a buster collar or medical shirt for a few days after they are neutered to protect their wound. If your dog licks or damages their wound they might develop an infection or cause the wound to open up.

Will neutering stop my dog humping?

There are many reasons why dogs hump; sometimes because of hormones, but also because of excitement or habit. For more information, read our article on humping behaviour in dogs, and speak to your vet to discuss whether neutering might help.

Is it too late to neuter my older dog?

No, in most cases neutering is a very safe and worthwhile operation, regardless of age. 

My dog has accidentally mated, what should I do?

If your dog has accidentally mated, contact your vet to discuss your options.

Can pregnant dogs be neutered?

Yes, in many cases it is possible to spay a pregnant dog. If you think your dog might be pregnant, contact your vet as soon as possible to discuss your options.

Can I neuter my dog before her first season?

Yes, your dog can be neutered before her first season. In fact, neutering a female dog before her first season significantly reduces the risk of certain medical conditions such as mammary (breast) cancers and pyometra (womb infection).

What is a laparoscopic (lap) spay?

A laparoscopic spay (lap spay) is when a dog is spayed via keyhole surgery.  Lap spays create much smaller wounds, tend to be less invasive, and reduce the risk of certain complications. However, at present, they are only performed by certain vets, and require special equipment, so aren’t available everywhere.

I have an unneutered female and male dog, what should I do to avoid an unwanted pregnancy?

If you have an unneutered male and female in the same household, it’s a good idea to consider neutering one or both of them. If this isn’t possible, you will need to keep them completely separate for 2-4 weeks every time your female dog is in season. They will both want to get to each other, so you will need to keep them distracted and in secure areas. If possible, it may be easier for someone else to look after your male dog while your female is in season.  

Will dog siblings mate?

Dogs aren’t selective about who they mate with, and given the opportunity will mate with their siblings. Their offspring would be closely related, and could have serious health problems. If your pets accidentally mate and they’re related, contact your vet as soon as possible – or better still get them neutered before any accidents happen.

Will neutering give my dog cancer?

Neutering won’t give your dog cancer – in fact neutering reduces the risk of many types of cancer. There are people who believe that neutering can increase the risk of certain cancers, but there is no solid evidence for this despite lots of scientific studies. As neutered dogs tend to live longer than un-neutered dogs, it may be that any increase in cancer rates we see are related to the longer lifespan, instead of neutering.

Published: February 2022

Written by vets and vet nurses. This advice is for UK pets only. Illustrations by Samantha Elmhurst.