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When to Spay or Neuter a Dog or Cat: Ages, Benefits and Risks

The right age to spay or neuter depends on species and adult size. AAHA guidance for cats and small and large dogs, plus benefits, risks and recovery.

Updated October 2026 · 8 min read · By the Hushku editorial team · 2 sources

Short answer

AAHA guidance: neuter or spay cats by 5 months of age. Small-breed dogs (under about 45 lb or 20 kg as adults) can be neutered at about 6 months or spayed before their first heat (5 to 6 months). Large-breed dogs are usually neutered after growth stops (9 to 15 months), and large-breed females spayed between 5 and 15 months, depending on their risks. Talk to your vet about your pet.

Key facts

  • Cats: neuter by 5 months old.
  • Small dogs (under ~45 lb as adults): neuter at about 6 months or spay before the first heat.
  • Large dogs: males after growth stops (9–15 months); females between 5 and 15 months, by risk.
  • Neutered pets need about 10–20% fewer calories.

Definition

Spaying (ovariohysterectomy or ovariectomy) removes a female's ovaries, and usually the uterus. Neutering (castration) removes a male's testicles. Both prevent pregnancy and change hormone-related behaviour and disease risk.

For decades, almost all pets were neutered at around six months. Research on large-breed dogs has since shown that timing can affect the risk of some joint problems and cancers, so advice now depends on species, size and sex. For cats, earlier neutering is recommended to prevent unplanned litters and spraying.

There's no single right age for every dog. The decision balances the risk of unwanted litters, behaviour, mammary cancer and womb infection (pyometra) against orthopaedic and other risks in some breeds. Your vet can help weigh these for your pet.

Benefits

  • Prevents unplanned litters
  • Spaying removes the risk of pyometra (womb infection) and greatly reduces mammary tumours if done early
  • Neutering removes the risk of testicular cancer and reduces roaming and some marking behaviour
  • In cats, reduces spraying, fighting and roaming

Risks and trade-offs

  • General anaesthetic and surgical risk, which is low in healthy young pets
  • Increased tendency to gain weight: feed about 10 to 20% less and keep an eye on body condition
  • In some large breeds, early neutering has been linked to a higher risk of joint disorders and some cancers, which is why timing is later
  • Urinary incontinence in some spayed females, usually treatable

Recovery

Most pets go home the same day. Expect 10 to 14 days of restricted activity, a cone or body suit to stop licking, and a wound check. Call your vet if the wound is swollen, oozing or open, or if your pet isn't eating.

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Sources

  1. AAHA: When should I spay or neuter my pet?
  2. AVMA: Spay and neuter brochure

We check guides against veterinary sources and update them when guidance changes. How we write and review.

Questions.

Should I let my dog have one litter or one season first?

There's no health benefit to letting a dog have a litter. Spaying before the first heat gives the biggest reduction in mammary cancer risk in small dogs; for large breeds your vet may advise waiting.

Will neutering change my dog's personality?

It reduces some hormone-driven behaviours, such as roaming and mounting, but doesn't change basic personality or make dogs less protective.

Will my pet get fat after neutering?

Neutered pets need fewer calories. Reduce food by about 10 to 20% and monitor weight; weight gain isn't inevitable.

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