Dogs don’t have “periods” exactly like humans, but their heat (estrous) cycle with bleeding usually lasts about 2–4 weeks in total, with visible spotting often around 10–14 days.

Basic timeline

  • Most female dogs bleed and show heat signs for roughly 2–3 weeks, though some are as short as 2 weeks and others closer to 4 weeks.
  • The most fertile time is usually in the middle of that window, when bleeding often becomes lighter or more watery.
  • Many dogs go into heat about twice a year, but small breeds may cycle more often and giant breeds less often.

Stages of a dog’s “period”

  • Proestrus : First 7–10 days on average; vulva is swollen, blood-tinged discharge is obvious, males are attracted but she typically won’t accept mating.
  • Estrus (heat) : Around 5–10 days on average; bleeding often lessens or changes color, and this is when she is receptive and can get pregnant.
  • Afterward, the body returns to a resting phase until the next cycle, which is usually several months away.

When it starts and how often

  • Many dogs have their first heat at about 6–12 months old, though large and giant breeds can be later.
  • On average, heat happens every 6–7 months, but the interval can be as short as 4 months or more than a year depending on size and breed.

When to call the vet

  • Bleeding that lasts much longer than 4 weeks, is extremely heavy, or comes with lethargy, fever, or foul-smelling discharge needs urgent vet attention.
  • If you do not plan to breed your dog, spaying prevents heat cycles and lowers the risk of serious uterine infections and some cancers.

Bottom line: most dogs’ “periods” (heat with bleeding) last around 2–4 weeks, and they usually happen about twice a year, but individual and breed differences are normal.