Female dogs do not have a monthly period like humans, but they do have “heat” cycles where they bleed. This usually starts when they reach puberty.
When it first happens
Most female dogs get their first heat (their version of a period) at about 6 months old, but there is a wide normal range. Small breeds may come into heat as early as 4–6 months, while large and giant breeds may not have their first heat until around 12–18 months or even up to 2 years of age. If a dog has not come into heat by about 2 years old, a vet visit is recommended to make sure everything is normal.
How often and how long
After the first heat, most dogs come into heat about every 6 months, though small breeds can cycle 3–4 times a year and giant breeds sometimes only once a year. The visible “bleeding” part of the cycle usually lasts around 2–3 weeks, with total heat signs often lasting roughly 2–4 weeks.
Signs to watch for
Common signs that a female dog is in heat include a swollen vulva, bloody or pink discharge, increased urination, and changes in behavior such as restlessness or seeking male dogs. During this time she can get pregnant, so unplanned mating should be prevented if you do not plan to breed her.
