Best Age to Desex a Dog: Health Risks, Breed Differences & What Every Owner Should Know

   Deciding the best age to desex a dog is a hot topic for Australian pet owners, breeders, and vets alike. Should you desex your puppy before their first heat, or is it safer to wait? What are the health risks of early vs late desexing, especially for large breed dogs? In this evidence-based guide, I’ll break down the pros and cons, answer common questions about desexing timing, and share practical advice for supporting your dog’s joint health, immune system, and overall wellbeing—no matter when they were desexed.

What is the Optimal Age to Desex a Puppy or Dog?

There’s no universal “best age.” The ideal timing depends on your dog’s breed, size, sex, and health. New studies show that waiting until full maturity -especially for medium, large, and giant breeds - leads to better joint health and fewer orthopaedic problems. Small breeds may be suitable for earlier desexing, but it’s always best to tailor your approach.

Myths & Outdated Advice About Desexing (Spaying/Neutering)

Despite advances in research, many myths about desexing still circulate in the dog world - passed down from breeders, trainers, and even some veterinary professionals. Let’s clear up the most common misconceptions, so you can make decisions based on science, not tradition.

Myth 1: “Six months is always the best age to desex.”

• Fact: There’s no universal “best age.” The ideal timing depends on your dog’s breed, size, sex, and health. Waiting until full maturity (16 months-36 months) is especially important for large breed dogs.

Myth 2: “Early desexing prevents all cancers.”

• Fact: While early desexing can reduce the risk of mammary tumours in females (if done before the first season), it also increases the risk of other cancers - like osteosarcoma, lymphoma, and hemangiosarcoma - especially in certain breeds. Sex hormones play a critical role in keeping the immune system strong and vigilant, helping it hunt down and destroy abnormal cells, including cancer cells. Without these hormones, the body may be less effective at preventing some types of cancer from developing.

Myth 3: “Desexing solves all behavior problems.”

• Fact: Desexing may reduce some hormone-driven behaviors (like roaming or marking), but it’s not a cure-all for aggression, anxiety, or reactivity. In some cases, early desexing can even increase anxiety or fear-based behaviors. Training and socialisation are just as important.

Myth 4: “If you don’t desex, your dog will definitely develop health problems.”

• Fact: Keeping dogs entire can increase the risk of certain issues (like mammary cancer or pyometra in females), but with regular check-ups and responsible management, many dogs remain healthy for years without any issues at all. And let’s be honest - do we desex humans once they pass puberty just because there’s a risk of testicular cancer in men or cervical cancer in women? Of course not! It’s about balancing risk, not eliminating it entirely.

Myth 5: “All vets and breeders agree on desexing timing.”

• Fact: There’s still debate, and recommendations are changing as new evidence emerges. The best vets tailor their advice to your dog’s unique situation, not a one-size-fits-all rule.

Remember: The best decisions are made with up-to-date science, an open mind, and your dog’s individual needs at the center.

Health Risks of Early Desexing (Spay/Neuter)

While desexing has its place in responsible pet ownership, performing the surgery too early - often before 6 months of age - can carry significant risks that many owners aren’t told about upfront. Here’s what the latest science (and my own experience) reveals:

Joint Problems After Desexing

• Growth Plate Closure: Early desexing delays the closure of growth plates, resulting in longer, thinner bones and altered joint angles. This can lead to a higher risk of hip dysplasia, elbow dysplasia, and especially cruciate ligament injuries.

• Real-Life Example: I’ve seen far more cruciate ligament injuries in dogs desexed before maturity than in those left entire or desexed later. Dogs desexed after full maturity tend to have stronger, more stable joints.

Urinary Incontinence After Spay

• Hormonal Impact: Estrogen is vital for urinary tract health. Removing the ovaries too early can disrupt normal development, leading to weak bladder control.

• Clinic Story: A Cavoodle desexed at 8 weeks developed lifelong urinary incontinence, needing herbal hormone support for over a year. Not all recover fully.

Cancer Risk After Spaying/Neutering

• Immune System Role: Sex hormones help keep the immune system in top shape, hunting down and destroying abnormal cells - including cancer cells. Early desexing reduces this protection, raising the risk of cancers like osteosarcoma, lymphoma, and hemangiosarcoma, especially in some breeds such as German Shepherds, Rottweilers, and Burmese Mountain Dogs.

• Scientific Evidence: Multiple studies have found higher cancer rates in dogs desexed before 12 months, particularly in large and giant breeds.

Musculoskeletal & Behavioral Effects

• Muscle Mass and Frame: Testosterone and estrogen drive the development of strong muscles and a balanced frame. Early desexed dogs often have thinner bodies and less muscle.

• Clinic Story: Comparing two puppies—one desexed at 6 months, the other at 24 months—the later-desexed dog was noticeably stronger, with better angulation and muscle mass.

• Confidence & Coping: Early desexing can sometimes increase anxiety, fearfulness, or reactivity, as hormones play a role in brain development and emotional regulation.

Other Health Risks

• Obesity: Early desexed dogs are at higher risk of weight gain, which can compound joint and metabolic issues.

• Endocrine and Immune Disorders: Emerging evidence suggests increased risk of certain autoimmune and endocrine diseases (e.g., hypothyroidism).

Bottom line: Early desexing can lead to a range of preventable health issues. Many are best avoided by waiting until your puppy has reached full physical maturity—especially for medium, large, and giant breeds.

Health Risks of Keeping Dogs Entire (Not Desexed)

While waiting to desex (or choosing not to at all) can offer important health benefits, keeping dogs entire isn’t risk-free either. Here’s what you need to know:

Pros and Cons of NOT Desexing

• Females: The risk of mammary (breast) cancer increases with each season a female dog goes through without being desexed. Pyometra—a potentially life-threatening infection of the uterus—also becomes more likely, especially as dogs age.

• Males: Entire males have a higher risk of testicular cancer (which is eliminated by desexing) and prostate problems later in life. However, these conditions are often manageable with regular check-ups and prompt treatment.

Accidental Pregnancies

Keeping dogs entire increases the risk of accidental matings and unwanted puppies—a major contributor to shelter populations. Responsible management and supervision are essential.

Behavioral Changes After Desexing vs. Not Desexing

• Roaming & Marking: Entire males are more likely to roam, mark territory, and display hormone-driven behaviours. Some entire females may show changes during their heat cycles.

•  Only a small percentage of entire males actually develop behavioural issues, and 
  
  in my experience, lack of training is usually a bigger contributor. Some of my favourite dogs I see in the clinic are entire males—and they have the most gentle, gorgeous temperaments (shout out to Turner, Maverick and Astro!). In my opinion, training and familial genes play a much stronger role in behaviour than whether a dog is entire or not.

Extra Care Needed

• Entire dogs require more attentive management—regular health checks, monitoring for reproductive issues, and careful supervision to prevent unwanted breeding.

The bottom line: Keeping your dog entire isn’t necessarily “dangerous,” but it does come with its own set of risks and responsibilities. With good management, many of these risks can be minimized.

Supporting Dogs Desexed Early: Joint, Immune & Diet Tips

If your dog or puppy was desexed early—whether by choice, shelter policy, or breeder requirement—don’t panic! There’s plenty you can do to help them thrive and manage potential long-term health risks.

Joint Supplements for Desexed Dogs

• Support healthy cartilage and ligaments with supplements like glucosamine, collagen, and MSM (methylsulfonylmethane). MSM is particularly helpful for ligament strength.

• Add bones or a sprinkle of crushed eggshell to meals for a boost of naturally occurring calcium.

  

• Tip: Our Joint Protect formula combines MSM, collagen, fish oil, rosehip, turmeric, and boswellia and other key ingredients for joint health (no hard sell—just sharing what works in clinic!).

Immune Support for Dogs

• Support immune vigilance with herbs like turkey tail mushroom, ganoderma, and cordyceps (my favourite for immune support!).

• Ensure a balanced intake of zinc, selenium, and other trace minerals.

• Tip: Our Immune Support blend features these mushrooms and more if you;re after a All-In-One immune support supplement. If you're keen and wish to delve into research and find the ingredients that your pup may need, you can also use single-ingredient powders for a DIY approach.

Keeping Them Fit and Healthy

• Movement is medicine! Keep your dog at a healthy weight and maintain muscle tone with daily walks, play, and age-appropriate activities.

Diet for Desexed Dogs

• A diet rich in quality animal protein and low in processed carbs supports the hormonal system and helps manage weight. Consider rotating protein sources and including organ meats for extra nutrition.

Remember: Early desexing doesn’t mean your dog is destined for health problems—it just means they may need a little extra support.

Summary & Decision Guide: When Should I Desex My Puppy?

Choosing when (or if) to desex your dog is a big decision—and there’s no single answer that fits every dog or family. Here’s how to weigh up the evidence and make a confident, informed choice:

Key Considerations

• Breed & Size

• Sex- male or female.

• Lifestyle

• Health History and conditions the breed is susceptible to.

• Your Goals

Decision-Making Tips

1. Talk to Your Vet

2. Don’t Rush

3. Consider New Alternatives

4. Remember Your Dog’s Uniqueness

Desexing Age by Breed Chart / FAQ

• What are the risks and benefits of desexing at different ages for my dog’s breed and size?

• Are there new surgical alternatives that might be suitable? Currently, there are specialist vets that are now offering hysterectomies (removal of uterus, but keeping the ovaries attached and healthy), and vasectomies (keeping the testicles, but cutting the tubes that allow the sperm to travel). Could this be an option for you to consider?

• How can I best manage an entire dog if I choose to wait?

Final word: The best decisions are made with all the information you can gather, evidence, and taking into account your needs and the environment they will be living in. But always remember: we all make decisions with the best information we have at the time, so if the timing that was chosen for desexing was not ideal, it's not the end of the world, they just may need extra support.

Questions About Desexing Timing or Breed-Specific Concerns? Ask Below!

Still unsure about the best timing for your pup? Wondering what’s most important for your dog’s breed or situation?

Drop your questions in the comments section below the blog—I read and reply to every one. Whether you’re a first-time dog owner or a seasoned breeder, I’m here to help you make the best decision for your furry family member.

No question is too big or too small—let’s make sense of the science together! 🐾

References & Further Reading on Desexing Age, Health Risks, and Alternatives

1. Long-Term Health Effects of Neutering Dogs: Comparison of Labrador Retrievers with Golden Retrievers

Hart BL, Hart LA, Thigpen AP, Willits NH.PLOS ONE, 2014.Read the study

2. Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas

Zink MC, Farhoody P, Elser SE, Ruffini LD, Gibbons TA, Rieger RH.Journal of the American Veterinary Medical Association, 2014.Read the study

3. Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers

Hart BL, Hart LA, Thigpen AP, Willits NH.PLOS ONE, 2013.Read the study

4. Determining the optimal age for gonadectomy of dogs and cats

Spain CV, Scarlett JM, Houpt KA.Journal of the American Veterinary Medical Association, 2004.Read the study

5. The effect of neutering on the risk of mammary tumours in dogs—a systematic review

Beauvais W, Cardwell JM, Brodbelt DC.BMC Veterinary Research, 2012.Read the study

6. Early spay-neuter clinical considerations

Kustritz MVR.Clinical Theriogenology, 2012.Read the article

7. Endocrine and metabolic changes after gonadectomy

Root Kustritz MV.The Veterinary Clinics of North America: Small Animal Practice, 2013.Read the abstract

8. Canine gonadectomy (spay/neuter) debate: Population control, health, and behavior

Zink MC.Theriogenology, 2005.Read the abstract