Dogs typically go into heat about twice a year, approximately every 6 to 7 months, though this can vary depending on the dog's breed, size, and age. Small breeds tend to have their first heat earlier, around 6 months old, while larger breeds may not experience their first heat until 12 to 16 months or even up to 2 years of age
. Each heat cycle usually lasts around 2 to 4 weeks (14 to 21 days), during which the dog is fertile and can become pregnant. The cycle includes phases such as proestrus (beginning with swelling and bleeding), estrus (when the dog is receptive to mating), and anestrus (a resting phase)
. Some breeds, like Basenjis, Tibetan Mastiffs, and Dingoes, may go into heat only once a year. As dogs age, the intervals between heat cycles may lengthen, but female dogs do not experience menopause and can continue to go into heat throughout their lives unless spayed
. In summary:
- Frequency: About every 6 to 7 months (twice a year on average)
- Duration: About 2 to 4 weeks per heat cycle
- First heat: Usually around 6 months old for small breeds, later for larger breeds
- Variation: Some breeds cycle once a year; intervals may lengthen with age
Spaying a female dog stops the heat cycles altogether and prevents pregnancy
