Female dogs usually start their “period” (heat) around 6 months old, but it can be earlier or much later depending on size and breed. Small breeds often start closer to 6 months, while very large breeds may not come into heat until 18–24 months.

Quick Scoop

  • What it really is: Dogs don’t have periods like humans; they have an estrous (heat) cycle, where you’ll see bloody discharge, a swollen vulva, and interest from male dogs.
  • Typical first age:
    • Small breeds: around 6–9 months.
* Medium breeds: around 6–12 months.

* Large/giant breeds: often 12–24 months.
  • How long it lasts: The visible “period” part (bleeding/heat) usually lasts about 2–3 weeks, sometimes up to 4.
  • How often it happens: Most female dogs come into heat about every 6 months, though some small breeds cycle 3–4 times a year and some giant breeds only once a year.

What you’ll notice

  • Spots of blood or pink discharge on bedding or the floor.
  • Swollen vulva and more frequent licking of that area.
  • Behavior shifts: clingy or restless, more interested in going outside, and male dogs suddenly very interested in her.

What you should do

  • Keep her away from unneutered males during heat to avoid pregnancy.
  • Use washable blankets, doggy diapers, and gentle wipes to manage hygiene and cleanup.
  • Call a vet if:
    • She hasn’t had a first heat by around 2 years (especially in large breeds).
* Discharge smells very bad, is pus-like, or she seems sick (tired, not eating, drinking a lot), as this can signal a serious uterine infection called pyometra.

Spaying and timing

  • Vets often recommend spaying either before the first heat or between heats, depending on your dog’s size, breed, and local guidelines.
  • Spaying stops future heats entirely and helps prevent certain cancers and uterine infections later in life.

Bottom line: most dogs start their “period” around 6 months, but any time between 6–24 months can be normal, and a vet visit is the best way to get breed‑specific advice for your dog.

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