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Spaying and Neutering Your Pet – How long do you wait?

Written By Dr. Alyssa Dayton, DVM

How do you know when is the right time to spay or neuter your pet? This topic has been debated about time and time again amongst the veterinary profession and pet owners, but when it comes down to it, it is a personal decision to make based on your own pet.

The first thing to address is the importance of sterilization in the companion animal world, regardless of age. The biggest reason to do it from a shelter-based point of view is population control. In just the state of Florida, in 2020 there were over 250,000 animal intakes. That’s 250,000 animals that are looking for new homes, many of which are from unintended litters of puppies and kittens. All of these animals require time and resources from the organizations to place them in new loving homes and medically treat them as needed.

From an individual pet health perspective, there are many more benefits to spay/neuter than there are to keeping them intact. A common emergency seen in intact female animals is a pyometra, an infection of the uterus. This infection can happen at any age, and usually occurs soon after a heat cycle has ended. This type of infection can be life-threatening and the treatment can cost thousands of dollars at an emergency facility. In male dogs left intact, the levels of testosterone in their bodies can lead to enlargement of the prostate, a painful condition that cannot be left untreated. In both genders, there are often behavioral effects of being left intact as well, including marking furniture with urine, escaping yards to chase smells, aggression to humans and animals, and many more. In the end, there are few to no benefits to leaving animals intact their entire lives. But when is the best age to have the procedure done?

Spaying/Neutering at a young age (<6 months)


In female dogs, 25% of intact female dogs will develop mammary cancer. If the spay is performed before their first heat cycle (around 6 months old) – you essentially eliminate the risk of mammary cancer down to less than 1% of animals. If done after the first cycle, but before the age of 2yrs, the risk is still reduced to less than 10%. If you wait passed this point, there is minimal benefit to reducing mammary cancer.

Female cats show similar reduced cancer risk. If a cat is spayed before 6 months old, their risk of developing mammary cancer is 7x less than if left intact.

The procedure is relatively safer in younger animals due to the less developed reproductive organs and decreased risk of bleeding.

Male dogs that are left intact for a longer time are prone to perineal hernias, when the muscle wall of the pelvis weakens and becomes a thin area for abdominal organs to herniate through.

Less post-op complications occur in animals at a younger age. The animals tend to bounce back and recover faster and have less healing complications.

Decreased cost – often spay/neuter cost is based on the weight of the animal; an early procedure will help ensure a lower cost in larger breed animals.

Training at a young age can be easier with less hormones at play and can avoid potential aggression and territorial behavior before it occurs. It also can make house breaking/litter training your pet easier if the marking behavior is never allowed to start.


In giant breed dogs (over 90 lbs at full size), it may be beneficial to have the hormones in the dogs until they are full grown to help encourage joint health and normal bone anatomy. The research behind this has been controversial. Other factors that are known to be important for joint health are a healthy diet and preventing puppies from becoming overweight and getting too big too quickly.

Cosmetic appearance can be impacted by spaying/neutering early. In some breeds neutering early will prevent the male dogs from achieving the usual breed appearance in muscularity and head size, but this does not affect overall health.

Deciding when is best to spay/neuter your pet is a decision to be made for each pet owner with the help of their veterinarian. The points covered are just a few of the factors to consider when making the choice. The most important thing is that you do spay/neuter them at some point in their early life and to avoid accidental litters. As pet owners, it is vital to do everything within your control to give them a long healthy life with you and your family.