When Should I Spay or Neuter My Pet?

• Cats: Female kittens may enter their first heat cycle as young as four months, but usually not until they are five or six months old.  AAHA endorses the “Fix Felines by Five” initiative. It recommends sterilizing cats by five months of age. This helps prevent unwanted litters and greatly decrease mammary cancer risks in female cats as well as spraying/marking in male cats, but still allows kittens time to grow. Kittens sterilized at this age quickly bounce back from surgery.
• Dogs: One of the most common questions veterinarians hear is, “What is the best age to spay or neuter a dog?” The answer depends largely on your dog’s projected adult size and breed-related health risks. This is why the best age to spay or neuter a dog is not the same for every breed. The AAHA Canine Life Stage Guidelines  give different timing for small and large dogs. Small-breed dogs (under 45 pounds projected adult body weight) should be neutered at six months of age or spayed prior to the first heat (five to six months). Large-breed dogs (over 45 pounds projected adult body weight) should be neutered after growth stops, which usually is between 9 and 15 months of age. Many factors influence the decision on when to spay a large-breed female dog—your veterinarian can help narrow down the recommended window of 5 to 15 months depending on your dog’s disease risk and lifestyle.

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What are the benefits of spaying or neutering my pet?

Many pet owners think their female pet needs to experience the joy of motherhood at least once or that their male pet will feel less masculine if he’s neutered, but animals simply do not think that way. Pet owners also wonder if spaying or neutering will change their dog’s personality or calm behavioral issues such as spraying, roaming, or aggression.

US pet avoid  spaying or neutering their pets for a variety of reasons, including:

• They show or breed the animals
• Financial constraints
• Fear of anesthesia
• Lack of understanding of the benefits

These concerns might seem valid, but the reasons to spay or neuter far outweigh the risks of not doing so. Older show or breeding pets who are spayed or neutered can avoid various cancers and infections. Many spay-and-neuter clinics are low-cost and anesthesia in veterinary medicine now is on par with human medicine. If you’re still not convinced that spaying or neutering your pet can lead to a happier, healthier, longer life, consider these benefits:

• Spaying your female pet drastically slashes her risk of mammary cancer, which is fatal in about 50% of dogs and 90% of cats.
• Neutering your male pet eliminates his risk of testicular cancer.
• Spaying and neutering limits pet overpopulation.
• Spaying your female pet prevents heat cycles and eliminates yowling, crying, erratic behavior, and bloody vaginal discharge.
• Neutering your male pet reduces inappropriate behaviors, such as roaming to find a mate, marking inside your home, and fighting with other males.
• Spaying and neutering is more cost-effective than skipping the surgery. A uterine infection that requires emergency surgery to save your female pet’s life easily can cost several thousand dollars, while a simple tomcat neuter costs much less than products needed to eliminate urine odors after your home has been well-marked by your territorial male cat.

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What does research show about spaying and neutering pets?

Researchers still have limited data on the exact age to spay and neuter pets, but emerging research informs AAHA’s guidelines. For example, cancer, orthopedic disease, behavioral problems, endocrine disorders, obesity, and urinary incontinence may be linked to sterilization status and the age at which the procedure is performed. The University of California, Davis, conducted a study on golden retrievers in 2013 that turned the world of veterinary medicine on its head concerning early spaying and neutering. Early sterilization prevented many issues, according to the study, but also appeared to increase the risk of other diseases, such as cranial cruciate ligament rupture, hemangiosarcoma, mast cell tumors, lymphosarcoma, and hip dysplasia. More research is needed, especially with different canine breeds, to help us understand the cause and effect of sterilization and the relationship between spay/neuter status and disease prevalence. More studies on the link between sterilization age and the onset of certain diseases also are needed.

How ongoing research informs spay and neuter recommendations

Ongoing veterinary research continues to explore how factors such as a dog’s breed, size, sex, and age at the time of sterilization may influence long-term health outcomes. Recent large-scale studies from university veterinary programs, including work from the University of California, Davis, highlight that sterilization timing is not a one-size-fits-all decision and that individual risk factors should be considered.

This growing body of research helps explain why current veterinary recommendations differentiate between small- and large-breed dogs and emphasize individualized decision-making. Rather than suggesting a single “best” age for all pets, these findings reinforce the importance of working with your veterinarian to determine the most appropriate timing based on your pet’s unique health profile. This is especially important for large and giant-breed dogs, whose growth patterns may influence the recommended timing.

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The decision about when to spay or neuter your pet is one you should make with your AAHA-accredited veterinarian. Because timing depends on your pet’s age, size, breed, and health risks, your veterinarian can recommend the safest and most beneficial window for sterilization based on AAHA’s latest canine and feline life stage and preventative care guidelines.

Article updated 2/5/2026