When Do Female Puppies Start Going Through Heat?

Your female puppy's heat cycle can start well before she's an adult, particularly if she's an itty-bitty breed. Spaying her early enables you to avoid the start of heat -- even the first cycle.

All About Size

Smaller breeds enter adolescence earlier than larger breeds. The littler canines typically go through first estrus around 6 months of age. The largest breeds can go as long as 24 months before their first heat cycle begins. Margaret Root Kustritz, veterinarian and professor at the University of Minnesota College of Veterinary Medicine, notes that, on average, first estrus begins in female puppies between 10 and 12 months.


Heat brings increased urination, vaginal discharge and tendency to mark indoors and outside. Plus, your puppy is at risk of becoming pregnant. Spaying your puppy early stops her from going into heat and eliminates these risks and inconveniences. The American Society for the Prevention of Cruelty to Animals notes that vets can spay female puppies at 2 months of age, which means you can typically prevent your puppy's first encounter with estrus altogether.