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Dogs in Heat

Profile photo of Heather Venkat, DVM, MPH.By Heather Venkat, DVM, MPH, DACVPM

Jump to:
How do I know if a dog is in heat?
How long does a dog stay in heat?
When do dogs go into heat?
What is happening during a dog heat cycle?
What if my dog doesn’t get pregnant?
Should I use artificial insemination?
If my bitch conceives, how large will the litter be?
Should I spay and neuter to prevent dogs in heat?
Consult your vet

Below we cover the essentials you need to know about dogs in heat.

From knowing how to tell if your female is in heat to understanding the different stages of a female’s heat cycle and beyond, it’s time you’re in the know.



Perhaps you’re a new dog breeder digging for knowledge about dogs in heat.

You’ve heard the term but the definition has you stumped.

Or maybe you know the process.  You’re simply wondering when or how often you should expect it to happen for your bitch.

And how will you even know when it’s happening?

Or perhaps you are a concerned parent who is wondering if you should be worried about your dog’s recent discharge of blood.

Wondering if something is grossly wrong with your beautiful canine, you’re scouring the internet for answers.

Either way, unless you have previously neutered your female dog, dog pregnancy and dogs in heat are frequent terms and a natural reality inside a dog owner’s world.

There is no need to stress over that seasonal discharge.

Instead, simply grab a few doggy diapers or a cleaning rag and get ready to clean a few messes.

How Do I Know if a Dog is in Heat?

When a dog goes ‘in heat’, it simply means she is undergoing a natural female cycle.

During this cycle, an expert can breed a canine female with the hope of producing a family of cute little puppers.

You’ll know your dog is in heat when she begins discharging blood.

If you’re on the alert, you can also predict when your bitch is about to go into heat by watching her bottom.

A bitch’s bottom will swell as her heat cycle approaches.

Also keep an eye on the local male dogs as they become intensely attracted to female dogs in heat.  

If you have a specific breeding plan, you will want to supervise your bitch in heat every time she goes outside to prevent any unwanted males from jumping the fence, or from your female escaping to chase after that tempting male dog.


Once the blood discharge begins, take note of the exact day it starts.

Timing is everything when mating your bitch with a sire.

If a litter of pups is not your desire, simply keep those males away and enjoy another season just you and dog, without any new little puppers.

Unfortunately, siblings and family dogs will mate on their own, so if you also own intact male dogs, simply keep them separated from your female to avoid unwanted inbreeding. 


Is My Dog in Heat Infographic

How Long Does a Dog Stay in Heat?  

Dogs in heat will typically stay in heat between 18 – 24 days.

Additionally unless neutered, a female dog will naturally experience her heat cycle twice a year.

Professionals consider a bitch ‘in heat’ anytime during the heat cycle.


When do Dogs Go Into Heat? 

A bitch (female dog) typically goes in heat twice a year, once in the Spring and again in the Fall.

A dog’s very first heat cycle can occur any time between six and twenty-four months of age and will vary between individual dogs, female sizes and particular breeds.

Generally smaller breeds will experience their first heat younger than larger breeds.

To encourage optimum health in your bitch, never breed a female until at least her second heat cycle.  It’s important to ensure she can handle the rigor that pregnancy can have on her body.

Additionally, there are a plethora of factors influencing a dog in heat.

So while your dog may go into heat twice a year, remember every canine has the right to be unique.

Each dog will be different and every breed its own.

Once the cycle does begin for dogs in heat, it can last anywhere from eighteen to twenty-four days.


What is Happening During a Dog Heat Cycle?  

Dogs in heat progress through specific stages known as proestrus, estrus, and diestrus.


Stage One

During the first stage, known as proestrus, a bitch’s vulva (located just below the anus) will become swollen and bleeding will occur.

Bleeding will be your first obvious sign that your bitch is entering the heat cycle, and no need to worry about that discharge.

A bitch’s bleeding during her heat cycle is simply a vaginal discharge and can vary from slight to heavy bleeding.

During this stage the female may appear nervous and clingy, as well as sport a nesting behavior while collecting favorite toys and little things that bring her comfort in the sleeping area.

Urination will be frequent, her tail will be held close and the female will show no signs of wanting to breed.

Keep track of the exact day discharge begins as timing is key when breeding a bitch.



Around day seven, you might consider having your female tested to know exactly which days will be the best to breed your bitch.

You can either have your bitch tested by a veterinarian or if you’re a serious dog breeder, you could save some cash and learn the process yourself.

Camelot Farms supplies a “PreMate” test kit for breeders to conduct proper testing on dogs in heat without the assistance of a veterinarian.


Here is how you know when to breed your female dog.


With the test, blood is first withdrawn and submitted to a lab.

Inside the lab, the progesterone level is checked in the blood.

From these results a breeder can know on exactly which day a bitch will be most likely to conceive if bred.

In addition, Frawley offers a detailed explanation regarding how to interpret a dam’s progesterone level here.


Stage Two

Ten to twelve days after the initial discharge, stage two (known as estrus) is ushered in and your dog in heat is ready to breed.

The former bloody discharge will become clear or straw colored and your female will be quick to wag her tail to the side, thus making herself available to other male dogs (known as “flagging”).

She may begin licking her private parts, flirting with other male and female dogs and presenting her rump to dogs nearby in an effort to encourage their mounting her.

These sudden changes in behavior are simply a result of fluctuations in hormones.

Your female may also display a mounting behavior as she tries to mount other dogs, objects, hump pillows, stuffed toys or even your leg.

In addition, a female will give off pheromones which males can smell from a long distance away.

So be warned: if permitted, male dogs will come from far and wide in interest of your bitch.

Never leave a bitch alone in the yard for even a minute during this stage.


Stage Three

A bitch’s final stage in her heat cycle is diestrus.

During this stage, females are no longer interested in mating and their discharge is complete.

You’ll know the heat cycle is complete when there’s no more bleeding and the vulva will shrink back to its original size.

At this point, your female will have either a womb of little babes, encounter pseudo-pregnancy or be back to her previous normal self.

Pseudo-pregnancy, or false pregnancy, may occur four to nine weeks following a dam’s heat cycle.

If pseudo-pregnancy should occur, a female will show signs of pregnancy although she isn’t actually pregnant.



Symptoms of pseudo-pregnancy include a maternal behavior, nesting tendencies, vomiting, lactation, restlessness and an enlargement of the mammary glands.

These changes in behavior are again a result of hormonal changes and may occur even if a dam has not been mated.

What If My Dog Doesn’t Get Pregnant?

There is also the occasional bitch who encounters problems with breeding.

Should your bitch show no signs of swelling and only a little discharge, consider checking her thyroid levels.  She may need to get started on thyroid supplements.

The presence of cysts on the ovaries can also affect a female’s ability to become pregnant and may even require veterinary attention.

Or it could be an issue with the sire, which we’ll touch on below. 


Should I Use Artificial Insemination?

If distance constrains you from breeding your dam with the sire of your choice, say hello to artificial insemination.

Artificial insemination is an alternative form of breeding your dam with elite bloodlines.

With proper training, a dog owner can either conduct artificial insemination at home or visit the local veterinarian.

In conducting artificial insemination, experts collect semen from a sire and introduce it into a bitch’s reproductive organs.

The semen is initially gathered from a male dog while the sire and dam are together.

It is best for a sample of semen to be evaluated under a microscope to ensure optimum viability.

After all, a bitch might not become pregnant if the semen is unhealthy.

The breeder or veterinarian will check for motility (the number of swimming sperm vs non moving sperm), defects (how many sperm are intact are how many are defectively shaped or missing parts), and the number of total sperm (the more the better!).

Then while the female dog is in heat, a trained individual inserts the semen into the vagina or cervix through a plastic or glass straw.

Females are fully conscious through the entire process.

A second and extra sophisticated option for artificial insemination is endoscopic placement.

In endoscopic placement, certified experts sedate the female canine while placing a fine endoscope into the vagina.

The endoscope then guides a straw through the cervix and directly into the womb.

Endoscopic placement is a more invasive form of artificial insemination and should only be conducted by a certified veterinarian.


If My Bitch Conceives, How Large will the Litter Be?

There’s no absolute way to predict the size of a bitch’s next litter.

There are, however, factors which could be influencing how many darlings your female canine will be able to bear.

Typically larger breeds will carry larger litters as their sheer size is able to hold more little gems.

Smaller breeds, in contrast, will sport a reduced litter size.

For example, a Miniature Poodle carries an average litter size of three little pups.

In contrast, the towering Bullmastiff births an average of eight pups in a litter but wouldn’t be the first to introduce up to thirteen puppies to the world in a single day.


Phenomenally, an elite dog mommy will seldom birth more puppers than what her body is able to nurture.

As a result, diet becomes a serious factor.

An adult dog mom enjoying a healthy and nutritious menu will subsequently sport a well-fit body with increased fertility.

Her body will prove more capable of carrying and birthing a whole family of littles while following the birth, she’ll have lots of milk to share around with each darling pup.

A healthy dog-turned-mom is typically most fertile beginning with her second or third heat until she is four-five years old.

In addition, a female canine’s first litter will typically be smaller regardless the breed.

On a negative side, increased inbreeding will create a steady decline in litter size.

In addition, overbreeding or breeding too old of a dog can have the same effect of a smaller litter size as the dam’s body is no longer in optimum condition.



Should I Spay and Neuter to Prevent Dogs in Heat?

During a female’s heat cycle, things can get messy.

Your bitch doesn’t know to be discrete with things so her natural bloody discharge may find its way into many unwanted areas.

Whether it’s a stain on the carpet, a blotch on the bed, or residue left on the couch it is never pleasant to find your bitch’s discharge left throughout your home.  (Especially when Grandma is coming over!)

Some parents will wear doggy diapers on their bitch while others simply opt for lots of clean up sessions.

There is also the option of entirely eliminating a female dog’s heat cycle.

Call it neutering for males, spaying for females, or simply de-sexing, what you can expect is for pets to lose their sexual behaviors.

When spaying females specifically, a female dog’s ovaries and uterus are removed after which it will be impossible for her to go in heat.

Happier, Healthier Pets: The Benefits of Spaying & Neutering

From Visually.

She’ll no longer attract unwanted attention come Spring and Fall and you won’t stumble upon frequent discharge mess.

Litters will be zilch and your female will avoid specific behaviors accompanying sexually intact animals.


Consult Your Vet

Should you choose this route, be sure to first consult a reputable veterinarian to know when the best age is to neuter your dog.

Things aren’t all rosy with a neutered female, however.

A study done in UC Davis and published in 2013 reveals startling findings on the effects of neutering a pet.

Females who were neutered showed higher risks for diseases including:

  • Hip dysplasia (HD), an arthritis of the hip joint
  • Hemangiosarcoma (HAS), a cancer that could prove fatal
  • Lymphosarcoma (LSA), an immune system cancer which is often fatal
  • Mast cell tumors (MCT), yet another form of cancer

In addition, Falconer warns strongly against neutering dogs prematurely.  Certain growth hormones may be lost, creating problems as your pup develops from youngster to adult.

You would never consider giving your little baby girl a hysterectomy.

Likewise, be sure you don’t make that very same mistake on your young female dog.


Final Takeaways on Dogs in Heat

You alone know your dog best.

Whether it’s neutering, artificial insemination, mating your precious dam with a world-class sire or simply understanding that Spring and Fall heat cycle, enjoy your journey as you leverage the best decision for you and your prized canine.


Profile photo of the author Heather Venkat, DVM, MPH.Dr. Heather Venkat has been a veterinarian since 2013, working in companion animal medicine with dogs and cats, as well as veterinary public health. Her passion is in prevention, One Health, and strengthening the human-animal bond. A bonafide animal-lover, she competes in dog sports and currently shares her home with a border collie mix named Luna, three cats, and two leopard geckos.


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