The Heat is On: Recognizing your Dog's Estrus Cycle

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Perhaps you want to avoid putting your female dog in kennels when she's in heat. Or maybe you want to breed from her. Either way, understanding how a female dog cycles (and we’re not talking tandems) helps you plan.


It's also important to know what happens and when, so that you can avoid slips ups and mismatings. For example, recognizing when your female dog is coming into heat allows you to separate her from an entire brother and thus avoid the accidental patter of tiny paws.

When you understand a female's heat cycle, it's also easier to spot when something isn't right and get help from your vet. For certain problems, such as pus in the womb, this is  life-saving.

#1: What's Normal and What to Expect

The nitty gritty is that a female dog has a reproductive cycle twice a year (or every six months)--with give and take for individuals. This cycle involves a 3 to 4 week period 'in heat' when the body is getting ready to mate and prepares the womb for pregnancy. This heat period is subdivided into three:

  • Pro-estrus: Lasting 7 to 10 days, this is marked by a swollen vulva and bloody discharge. The female is interested in male dogs, but it's all about flirting rather than mating.

  • Estrus: Lasting 5 to 10 days, during this phase the female ovulates. Often the discharge becomes more scant, which can lull the unsuspecting owner into a false sense of security. Around that time she is very interested in males and will stand if mated.

  • Di-estrus: The hormones of heat ebb. The female is either pregnant or her hormone levels slowly reset themselves back to a resting level. Typically for a non-pregnant female the discharge occurs for another 7 to 14 days, then the vulva slowly shrinks down to normal size.

#2: Identifying Estrus (and Why it Matters)

Could your female pup be coming into estrus?

The timing of a female's first heat depends on her size (small dogs cycle at a younger age, say 6 months, whilst for giant breeds it's as late as 18 months). Also, the female needs to be fit and healthy to cycle, as her body's ultimate aim is to have puppies.

The signs to look for include:

  • Behavior changes: Your normally coy girlie becomes all flirtatious, whilst some loving girls get quite grouchy. If there's a strange change in her behavior - think "Could she be coming into heat?"

  • A swollen vulva: If you're not sure - take a photograph, and then another several days later for comparison. The vulva can look alarming enlarged in some dogs, but this is nothing to worry about.

  • A discharge: As the wombs revs up, a bloody discharge is anticipated. Some dogs lick this away in the early stages. If you want to be sure about the heat, place a white pillow slip on her bed to spot telltale signs of a discharge.

  • Vet checks: There are tests your vet can perform to identify the stage of the cycle. These include vaginal cytology (examining cell smears under the microscope) or blood tests.

#3: When things Go Wrong

Coming into heat is normal, and your dog should remain well. If she is in heat but is unwell, then speak to your vet immediately.


Of great concern is the female who has a vaginal discharge when she's not due in heat. This could be a sign of a womb infection. Other warning signs include:

  • Increased thirst

  • Lack of appetite

  • Lethargy

  • Vomiting

  • A raised temperature.

If you are in the least suspicious that something isn't right, contact a vet as a matter of urgency. Pus in the womb ('pyometra') is a serious condition which needs urgent treatment

And finally….

Know that it's an old wive's tale that a female dog should have a litter before being neutered - This simply is not the case. It's also an urban myth that a brother and sister dog won't mate...oh yes they will! So be cautious and separate siblings when the girl comes into heat.

Coming into heat is a big hormonal event for a female dog and some dogs become quite unsettled or distressed. Ultimately, getting her neutered is the best idea, so speak to your vet about the best time to go ahead for your precious pup.