Neuter or Not Neuter? A Vet’s Advice on What’s Right for Your Dog or Cat

Neuter or Not Neuter? A Vet’s Advice on What’s Right for Your Dog or Cat

Written by Alessandro Didiano (doctor in veterinary medicine, MRCVS)

Disclaimer: This article is personally written by me, a licensed veterinarian with more than a decade of clinical experience. It’s for general information only and not a substitute for professional veterinary advice. Always consult a vet for health concerns or emergencies.

It was supposed to be a routine vaccination, one of those calm, straightforward appointments that feel like a welcome break after a hectic morning dealing with all sorts of animal illnesses. Lady, a 10-year-old Springer Spaniel, walked into the consult room with her owners, a friendly couple in their mid-thirties.

“How is Lady doing?” I asked.

“Very well!” they replied in unison.

“Is she eating and drinking normally?”

“Oh gosh, in the past week she’s been drinking all the time, much more than usual,” they said. “She must be hot.”

That explanation might have worked, if it hadn’t been October, and we weren’t in the UK. My inner ‘something’s-not-right’ alarm quietly went off. Dogs don’t usually get excessively thirsty just because they’re warm, especially not in the UK in autumn.

My mind started scanning possibilities: Diabetes? Kidney disease?

I began the physical exam, as I always do, checking the mouth, ears, eyes, moving down the body. And then, as I lifted her tail, I saw it: a small amount of greenish discharge coming from her vulva.

“Has she been spayed?” I asked, though in my mind. I already knew the answer.

One hour later, Lady was under general anaesthesia, and I was removing her uterus. The excessive thirst and vaginal discharge had been caused by a pyometra, a serious )and potentially life-threatening) uterine infection that’s surprisingly common in unspayed (entire) female dogs.

“How can a vaccination turn into emergency surgery?” asked Alice, the nurse assisting with the anaesthetic.

“Welcome to veterinary medicine, Alice,” I replied.

Neutering: A Common Yet Complex Choice

Neutering (spaying or castrating) is definitely the surgical procedure I perform the most as a clinical veterinarian, but it’s also one of the decisions that can feel most uncertain for pet owners.

I get asked this all the time in practice:

  • “Should I neuter my dog?”

  • “Is it really necessary to spay my cat?”

  • “What are the risks if I wait or if I do it too early?”

Honestly, I get it: there is so much contrasting information out there.  Plus, many people question the ethics of altering a normal biological function. I truly understand this, because I’ve asked myself these very same questions.

A Personal Note: My Early Doubts

When I was a young vet student, I really questioned the ethics of neutering. I wondered: Are we doing the right thing interfering with an animal’s biology like this? Shouldn’t we let them live naturally, without altering them to fit into our world?

But over time, the more I learned about animals through my studies, I had to face reality: we don’t live in an ideal world. We live in a world where millions of unwanted or stray animals end up in shelters every year. Sadly, some of them never make it out. And now, with pets living longer than ever before, they’re more likely to experience health issues linked to not being neutered (see Lady’s story at the beginning).

I realized that in today’s world, neutering is not just a medical decision: it’s often an act of compassion.

The Basics: What Is Neutering?

  • Spaying (females): Surgical removal of the ovaries, or ovaries plus uterus.

  • Castration (males): Surgical removal of the testicles.

In the last few years, veterinary medicine has also started offering chemical castration for male dogs, a non-surgical and temporary option (6 to 12 months) that can be ideal when surgery isn’t suitable or when owners prefer a reversible method in order to see the effects before committing to a definitive decision.

Pros and Cons: What I Tell My Clients

Why Neutering Can Be a Really Good Idea

The single biggest reason is population control. Preventing unwanted litters massively helps reduce suffering and overcrowded shelters.

Second, the health benefits. In females, it lowers the risk of mammary cancer and pyometra, the dangerous uterine infection I discussed earlier. In males, it prevents testicular cancer and can help with prostate issues. Also, certain types of anal gland tumors that are hormone-dependent often respond well to neutering, which reduces their risk or progression.

Finally, the behavioral benefits: Neutering reduces urine marking (all owners of 6 months-old unneutered male cats know this problem very well), roaming (again, male cats), dominance aggression, and sexual frustration.

But It’s Not Always One-Size-Fits-All

There are some drawbacks and situations where I suggest waiting, or sometimes skipping it entirely.

First of all, early neutering in large-breed dogs (like Labradors, Shepherds, etc.) can increase the risk of joint issues, such as hip dysplasia or cruciate ligament tears.

In Dachshunds, early neutering (before 1 year) has been linked to increased risk of IVDD (Intervertebral Disc Disease). IVDD in this breed is very common as it is, we don't have to increase the likelihood of it.

Also, weight gain is more likely post-neuter, especially if diet and exercise aren’t adjusted accordingly.

Finally, some studies suggest that bone cancers may have a slightly increased risk in certain dog breeds (mainly Rottweilers and other large or giant breeds) if neutered early, before 18 or even 24 months of age.

Timing Matters: When to Neuter

These are the guidelines I usually use:

  • Dogs:

    • Small breeds (under 20 kg): 6–9 months is usually fine.

    • Large breeds (over 20 kg): wait until 12–18 months to reduce joint risks.

    • Dachshunds: wait until at least 12 months to lower IVDD risk.

    • Rottweilers, German Shepherds, Retrievers: wait until 18–24 months to reduce bone cancer risk.

  • Cats: We usually advise to neuter both male and female cats around 5–6 months of age. Some shelters do it earlier, at 8–12 weeks, which is still considered safe. In cats, the main reason (apart from the health and behavioral benefits listed above) is the population control. Cats reproduce quickly and can contribute to a large stray or feral population if left unneutered, leading to overpopulation issues (and increased shelter intake)

When I Might Advise Not to Neuter — Or to Wait

If your dog has fearful or anxious behavior that could worsen after neutering; in many cases, hormones actually help and neutering can make the problem worse.

Also, if you’re planning to ethically and responsibly breed, with all the health testing and care that comes with it.

Finally, if your dog is male and you simply want to delay neutering, the risks are generally lower than with females. Just keep in mind that neutering might be necessary later in life if health issues like prostate disease or testicular problems develop.

Final Thoughts from a Vet Who’s Been There

I get why this feels like a big decision. You want to do what’s best for your pet. You want to protect their health and happiness. That’s what I want too!

After years in the field and hundreds (maybe thousands? I honestly don’t know) of these surgeries, neutering is one of the best tools we have for ensuring a better life, not just for our individual pets, but actually for animals as a whole!

But if in the past we used to to it blindly, now veterinary medicine is evolving. We now try to do it at the right time and for the right reasons. That’s where a vet’s guidance can make a difference. 

As always, if you have any questions or concerns, feel free to reach out. I’m always happy to help.