Most female dogs have their first heat (also called a “season”) at around 6 months old, but it can be as early as 4 months or as late as 2 years depending on size and breed. Small breeds tend to cycle earlier, while large and giant breeds often don’t come into heat until 12–24 months.

Typical age range

  • Common range: First heat usually appears between 6–12 months of age.
  • Small breeds: May come into heat as early as 4–6 months.
  • Large/giant breeds: Often first heat between 12–24 months, and some may be closer to 2 years.

How often and how long

  • Most dogs go into heat about twice a year, roughly every 6–7 months, though some small breeds can cycle more often and some large breeds only once a year.
  • Each heat usually lasts around 2–3 weeks, with bleeding and behavioral changes during that time.

Health and breeding considerations

  • Even though a dog can get pregnant on her first heat, veterinarians generally advise against breeding that early because her body is still maturing.
  • Spaying prevents heat cycles and helps reduce risks of pyometra (uterine infection) and some mammary tumors, but the ideal timing should be discussed with a vet for your dog’s breed and lifestyle.

Information gathered from public forums or data available on the internet and portrayed here.