How often do dogs go into heat?

Most female dogs come into heat about every six months, so twice a year. That’s the figure the American Kennel Club (AKC) gives, though individual dogs vary. Small breeds sometimes cycle a little more often, and larger dogs may cycle less often. A few breeds, such as the Basenji, cycle only once a year. If you’ve tracked a couple of heats, choose your own dog’s interval in the calculator for a better prediction.

First heats come anywhere from about 4 to 5 months in toy breeds to around 2 years in some giant breeds like Great Danes.

The four stages of the dog heat cycle

Stage	How long	What you’ll notice
Proestrus	About 9 days	Swollen vulva and bloody discharge. Males are interested, but she won’t accept them yet.
Estrus	About 9 days	Discharge lightens and may stop. She accepts males. Ovulation happens in this stage.
Diestrus	About 60 days	She’s either pregnant or her body behaves as if she might be. No longer receptive.
Anestrus	About 4–6 months	A resting phase until the next heat.

Those averages come from the AKC. The Merck Veterinary Manual gives typical ranges of 7 to 10 days for proestrus and 5 to 10 days for estrus, and the AKC notes either stage can run anywhere from 3 to 21 days in some dogs.

When is a dog most fertile?

Usually somewhere around days 10 to 14 after bleeding starts, early in estrus. That’s why the calculator highlights those days. But it’s an average, and it varies a lot from dog to dog and even heat to heat. The AKC notes that a dog’s fertile period runs from a couple of days before ovulation to about five days after.

If you’re planning a litter, don’t rely on dates. Vets time breeding with blood tests that track progesterone, which pinpoint ovulation far more accurately. If you’re avoiding a pregnancy, treat the whole heat as risky, from the first sign of bleeding until she’s fully out of estrus.

An example: Daisy’s last heat started on March 1, and she cycles about every six months. Her next heat should start around September 1. Proestrus would run to about September 9, estrus from about September 10 to 18, with her most fertile days likely around September 10 to 14.

Signs your dog is coming into heat

Swollen vulva and licking the area more
Bloody or straw-colored discharge
Peeing more often, sometimes marking
Restlessness, clinginess or mood changes
Sudden attention from male dogs

Small dogs sometimes have “silent” heats with very few signs, so track dates even if a heat seemed light.

When to see a vet

Bleeding that lasts much longer than three weeks
Heats less than about four months apart, or none by two years old
Pus-like discharge, drinking a lot, or seeming unwell a few weeks after a heat. These can be signs of pyometra, a serious womb infection that needs urgent care.

Common questions

How long does a dog stay in heat?

Usually about two to three weeks for the bleeding and receptive stages together (proestrus plus estrus), though it varies.

Can a dog get pregnant on the first day of heat?

It’s unlikely right at the start, but sperm can survive for days and timing varies, so keep her away from intact males for the whole heat.

Do dogs go through menopause?

No. Dogs keep cycling throughout life, though heats may become less frequent with age.

Does spaying stop heat cycles?

Yes. Spaying removes the ovaries, so she won’t come into heat again. Ask your vet about the best timing.

She’s been mated. When are the puppies due?

Use our dog pregnancy calculator to get the due date and a week-by-week timeline.

Sources

Last reviewed November 5, 2026.