Dogs are usually in heat (the fertile, “period-like” part of their cycle) for about 2–3 weeks, with most falling in the 12–21 day range.

Quick Scoop

  • Typical length: Most female dogs are in heat for around 14–21 days, though some are as short as 7–10 days and others closer to 28 days.
  • Bleeding time: Visible bloody discharge often lasts about 7–10 days, then becomes lighter or straw‑colored as ovulation and peak fertility hit.
  • Whole cycle vs “in heat”: The full estrous cycle has four stages and can stretch over months, but when people say “in heat,” they usually mean those 2–3 weeks when she has discharge and can get pregnant.
  • How often it happens: Most unspayed females cycle about every 6 months, but small dogs may cycle a bit more often and some large/giant breeds only once a year.

Mini breakdown of the stages

  1. Proestrus (pre-heat)
    • Lasts ~4–20 days.
    • Swollen vulva, bloody discharge, males are very interested but she often refuses mating.
  1. Estrus (true heat/fertile days)
    • Roughly 5–14 days, often overlapping with or following the heaviest bleeding.
 * Discharge usually lightens; this is when she will accept males and can get pregnant.
  1. Diestrus + Anestrus (after-heat and rest)
    • Diestrus can last up to ~2–3 months; hormones settle whether or not she is pregnant.
 * Anestrus is the quiet “off” period, often around 4 months, until the next cycle starts.

Signs your dog is in heat (and when it’s over)

  • More licking of the genital area, swollen vulva, bloody or pink discharge, more frequent urination, and extra friendliness or flirting with male dogs.
  • Heat is winding down when:
    • Discharge has nearly stopped.
    • Swelling goes down.
    • She and nearby males calm back to normal behavior.

Safety & home-care quick tips

  • Keep her away from intact males for the full 3–4 weeks to avoid surprise pregnancies; males can smell a female in heat from far away and can be very persistent.
  • Use:
    • Leash walks only (no dog parks).
    • Dog diapers or washable bedding for discharge.
    • Extra supervision at doors and in the yard.
  • Call a vet urgently if you see:
    • Very foul‑smelling discharge.
    • Lethargy, fever, or refusal to eat.
    • Extreme swelling or obvious pain.
      These can be signs of infection like pyometra, which is an emergency.

Little “forum-style” perspective

“My dog’s heat lasted almost a month from first spotting to when the males finally stopped hanging around the fence.” – A common type of story in dog forums, reflecting that 2–4 weeks is pretty normal.

TL;DR: When people ask “how long are dogs in heat for,” the practical answer is: expect about 2–3 weeks where she can attract and accept males, and plan for up to 4 weeks of management to be safe.

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