When should I spay or neuter my dog?

What changed in the recommendations

Through the 1990s and 2000s, spaying or neutering at 6 months was standard. Since 2013, a series of breed-specific studies (Golden Retriever, Labrador, German Shepherd, Vizsla, Rottweiler) have shown elevated rates of cruciate ligament rupture, hip dysplasia, and certain cancers (hemangiosarcoma, lymphoma, mast cell tumor) in dogs altered before skeletal maturity.

These findings are breed-dependent, they do not generalize cleanly to all dogs. Small breeds appear to tolerate earlier alteration better. The AVMA literature review summarizes the evidence and recommends individualized timing.

Rough guidance by size

• Small breeds (under 20 kg adult weight): 6–9 months is typically fine.
• Medium breeds (20–30 kg): 9–15 months, after growth plates close.
• Large and giant breeds (>30 kg): 12–24 months, with veterinary guidance for the specific breed.
• Females: weigh first-heat-cycle considerations (pyometra risk on the "wait" side vs mammary tumor risk on the "early" side).
• Behavior intact: most behavior issues attributed to entire dogs are training issues, not hormonal, alteration alone rarely solves them.

For cats, the calculus is different and simpler: alter by 5 months before sexual maturity is the joint AAFP/AVMA recommendation, primarily for population control and to prevent spraying.