Heat Cycle In Dogs: Everything You Need To Know

A Golden Retriever laying in bed happily, smiling with tongue out.

The majority of this article is written by a certified veterinarian.

Table of Contents

When female dogs reach maturity, they periodically enter a stage called the heat or estrus cycle. Their body undergoes several physical and hormonal changes to prepare for a potential pregnancy.

This process can take a toll on both the dog and their human’s health, making it vital that you learn how to manage your pet during this time.

This article will cover everything you should know about the canine heat cycle and what to do when your dog is in heat.

What Is The Canine Heat Cycle?

The “heat,” or estrus cycle is the reproductive cycle in a female dog. It’s the process in which a female dog can breed and become pregnant.

In some more informal cases, the heat cycle is also known as a dog period.

There are four stages of a dog’s heat: proestrus, estrus, diestrus, and anestrus.

A Pembroke Welsh Corgi sitting.

The “heat,” or estrus cycle is the reproductive cycle in a female dog. It’s the process in which a female dog can breed and become pregnant.

In some more informal cases, the heat cycle is also known as a dog period.

There are four stages of a dog’s heat: proestrus, estrus, diestrus, and anestrus.

A Pembroke Welsh Corgi sitting.

The 4 Stages of Dog Heat

Dogs undergo different physiological and behavioral changes in each stage:

1. Proestrus Stage

The Proestrus stage lasts anywhere from 0-27 days, but averages around 9 days.

This is usually where the owner starts to notice the changes associated with a dog in heat: The estrogen levels peak and male dogs are attracted, although females aren’t yet receptive.

Signs to Look For:
A swollen vulva and tinged blood discharge can be noticed.

2. Estrus Stage

The Estrus stage lasts from 4-24 days.

During this stage of the dog heat cycle, estrogen levels drop and the females become fertile and receptive to males.

Signs to Look For:
The vulva becomes enlarged and blood discharge decreases.

3. Diestrus Stage

This stage lasts about 2 months on average, and the female is no longer receptive to the male.

In the Diestrus stage, estrogen levels drop further, and progesterone levels peak for 3-4 weeks, regardless of the dog is pregnant or not.

4. Anestrus Stage

The Anestrus stage is usually 4 months long, although it can be longer in some breeds.

This stage lies between the diestrus and the next proestrus, where the uterus is being prepared for the next possible pregnancy.

There is no vulvar swelling or blood discharge in this stage.

How Long Does A Dog Stay In Heat?

Generally, between 2 and 4 weeks. 

This includes the dog’s proestrus and estrus stages (when they are bleeding or fertile) and lasts anywhere from 2 – 4 weeks collectively.

However, a dog’s heat cycle length can be shorter or longer depending on the breed. You can always ask your vet about your breed’s specific heat cycle length.

The true cycle begins with the swelling of the vulva and ends with the vulva returning to its normal size, so this time frame only includes these 2 stages.

As for the other 2 stages, the time of the diestrus stage depends on the status of the dog’s pregnancy (or no pregnancy), while anestrus is just the transition stage from one cycle to the next.

What Does It Mean When A Dog Is In Heat?

A female dog in heat is receptive to males and capable of mating and breeding.

Female dogs go through the heat cycle where they periodically release hormones to let other dogs know that they are fertile and able to conceive the puppies.

Dog heat can be prevented by spaying the dog. This is the simple term for a medical procedure called ovariohysterectomy. This surgical process removes the uterus and ovaries to sterilize a female do so she will also no longer be able to get pregnant.

If only the ovaries are removed, the procedure is known as ovariectomy.

Getting your dog spayed as early as possible is generally recommended, as it has several distinct health benefits. Additionally, it puts a leash on the overpopulation of pets.

In some large dog breeds, however, delaying the surgery is more beneficial than performing it early on.

Spayed Dogs and Heat

Spaying a dog prevents behaviors and situations during the estrus cycle that may be frustrating for the owner.

When dogs are in heat, they roam around to find a mate. Male dogs will also respond strongly to the pheromones from the female, and may display unusual behavior like pulling on a leash when they normally wouldn’t. This can cause problems for the owners of both female and male dogs. Spaying prevents female dogs from wandering out alone for this purpose or emitting those pheromones. 

Spaying also reduces the risk of breast cancer, pyometra, and uterine infections.

As for side effects, the procedure doesn’t affect a dog’s personality but may sometimes cause specific health problems:
Operating on large breeds before their growth is complete can lead to ligament tear. Additionally, having a dog sterilized (spayed or neutered) before their maturity increases the risk of noise phobia.

What if your spayed dog shows signs of heat?
Yes, some dogs show signs of heat even after spaying. This is most commonly due to ovarian remnant syndrome, where leftover ovarian tissue produces estrogen, the hormone responsible for dogs going into heat. It could also be due to the presence of accessory ovarian tissue.

Dogs with ovarian remnant syndrome are susceptible to the same health issues as non-spayed dogs.

Consult your vet to get a proper diagnosis of this syndrome if your spayed dog displays signs of heat such as a swollen vulva or bleeding.

How To Tell If A Dog Is In Heat?

The symptoms of a dog in heat range from physiological to behavioral changes. Hormones secreted cause the dog to act differently during the heat cycle as well as initiate some changes in their body.

These are some common behavioral and physical symptoms of a female dog in heat:

• Behavioral Changes

There are noticeable changes in a female dog’s behavior during heat. You may spot your dog becoming agitated or nervous and acting unusually, like snapping at you.

Don’t worry. Hormonal changes can cause your pet to become moodier during the estrus cycle.

Pups with an otherwise friendly personality can suddenly become aggressive, and this can be concerning for their unsuspecting families. It’s completely normal, and your dog will return to normal after their cycle.

• Swollen Vulva

If your dog has long hair, you might miss this symptom at first.

The vulva of a female dog becomes noticeably red and swollen during the estrus stage of the heat cycle. It also becomes itchy, so your dog may lick it excessively. For this reason, excessive licking of this swollen area is another sign of a dog period.

• Frequent Urination

Female dogs tend to urinate more frequently during the estrus stage of the dog estrus cycle, as the swelling of the genitals puts more pressure on the bladder.

They may even raise their legs differently while urinating. The dog will return to their normal routine once the cycle is over.

• Vaginal Discharge

In the first and second weeks of the estrus stage, dogs leak a bloody vaginal discharge.

Consider keeping your dog at home during this stage to avoid making a mess and to prevent an unwanted pregnancy.

By the end of the estrus stage, the discharge will turn less bloody and more watery. This is the most fertile period for a dog, so keep them safe.

• Mounting and Humping

Acting on instinct, your pooch may start mounting and humping anything they can find.

Be understanding if your dog does this. Remember, they are in their mating phase and only acting based on gut feelings aroused by hormones.

• Receptive To Male Dogs

As the fertile period of your female dog approaches, she may begin to flirt around with other dogs. This is part of the mating ritual.

Your pup might also display bolder behavior than usual, more likely to approach other animals.

• Position Of The Tail

You may notice your dog holding her tail one one side, up, or in some other odd position.

This is due to the swollen vulva and an indication to others that she is ready to mate.

• Loss Of Appetite

The discomfort during this time may cause your pup to become distant to food.

Loss of appetite can also be due to many other health conditions, so keep an eye out for more symptoms to determine if something other than heat is afoot. When in doubt, always contact your vet.

Do Dogs Bleed In Heat?

Yes, vaginal bleeding is one of the most common signs a dog is going into heat.

Some dogs bleed heavily, while others go through minimal discharge. Either way, don’t worry.

Vaginal bleeding mostly starts a few days into the estrus cycle, about 3 – 4 days after the start of the period.

• How Much Blood Is Normal For A Dog In Heat?

The amount of blood varies. Some dogs bleed heavily, and some bleed so little that you won’t even notice. The size of the dog matters here.

• How To Stop A Dog In Heat From Bleeding?

You can’t stop a dog from bleeding during heat, but you can take steps to manage it.

What to do about a dog in heat bleeding:
Buy some doggy diapers to prevent a mess and keep the dog off furniture, rugs, and carpets. Confine them to places that are soft and comfortable for them, but easy to clean for you.

A Bernese Mountain Dog Lying Down.

Do Dogs Get Cramps In Heat?

No, they shouldn’t. Although their behavior changes, dogs are usually not in pain during heat.

They become fidgety, but that’s just discomfort from physical and hormonal changes. If your dog seems to be in pain, consult a vet.

What To Do When Your Dog Is In Heat

You can take certain precautions to have a better experience with a female dog in heat. Here’s what to do when your dog is in heat and you don’t want to breed:

• Avoid Letting Your Dog Outside Alone

A male dog’s ability to find a female partner when she is emitting these pheromones is very high. If you let your female dog wander out alone in heat, chances are you will find some random male dog tied to her. Your female dog might escape the yard or enclosure, or a male dog could find its way into the yard, and pregnancy might ensue.

However, avoid isolating your dog during heat. Keeping her alone her all the time can be frustrating and might make your pup aggressive. The best option is to keep her busy with engaging activities like slow-feeding toys, play time with you, and finding other ways to entertain your dog.

• Keep Your Dog On-Leash

Never let your female dog off the leash during a heat, or period, even if she is well-trained and generally well-behaved.

Obedience to their owner tends to take a backseat once hormones take over and the female becomes instinctively intent on finding a male partner.

• Proper Exercise And Rest

Have a suitable exercise and rest schedule for your particular dog.

Some pups feel more tired during their heat, while others become overactive and fidgety. Keep an eye on your dog to learn what she needs and maintain a routine according to her specific needs.

• Consult A Vet

Of course, being in heat is not a disease, but some dogs may suffer certain illnesses like pyometra during a heat cycle.

Consult a vet if you notice any unusual symptoms not listed here, or if their behavior changes too much.

• Update ID Information

Make sure that your dog has an ID card attached to them with your most recent and updated contact information.

If your dog manages to escape during their heat, this ID card will help you reunite with them as soon as possible.

• Put Some Menthol On The Tip Of The Tail

This is an excellent trick to hide the scent of hormones.

If you must go outside, apply a small amount of menthol on the tip of the tail when taking your dog out. This is to prevent male dogs from smelling her from far away and approaching your female suddenly.

What To Do If You Want To Breed Your Dog

If you are planning on breeding your dog, keep these points in mind.

• Research

Several breeding methods are used today — research the best methods for you, what kind of dogs to breed and which breeder you’d like to get your dogs from in the first place.

Read books and really take your time — breeding comes with a lot of responsibility. You can even consult your vet about the pros and cons for your situation and your dogs.

• Choose Your Dogs And Examine Their Genetics

Make sure the breed and dog you choose for mating has a suitable male stud with good health. Check up on the general drawbacks of mating with certain breeds.

It’s vital to get the dogs you choose checked for possible health conditions; A healthy genetic pool with a great temperament is ideal.

• The Heat Cycle

Wait for your dog to go into her heat cycle for breeding.

Provide a comfortable environment while the female is going through her heat, and wait for the most fertile time of the cycle (when bleeding has mostly subsided).

Although it can vary, the best time for breeding is usually between the tenth and fourteenth day of the estrus stage of the heat cycle.

• Pregnancy And Post-Pregnancy Care

Know how to take care of a pregnant pooch and the care needed for a litter after delivery.

Have a whelping box ready and keep the pups warm once they are born. Also, always record information like the puppies’ date of birth and number of puppies.

A white Cockapoo Standing up next to a blanket.

When Do Dogs Go Into Their First Heat?

The first heat cycle in dogs occurs at puberty: for most dogs, this is around six months of age. 

For many other dogs, the first heat can vary depending on size and breed. Smaller dogs usually go into heat earlier than larger breeds. Very big dogs might not enter the estrus cycle until 18 months old or, in some cases, even until 2 years old.

How Often Do Dogs Go Into Heat?

Most dogs go into heat two times per year.

The dog heat season occurs about once every six months, but varies depending on several factors. Smaller breeds go into heat 3 times per year, while giant dogs go into heat only once per year.

Don’t worry if any young pup doesn’t follow one of these schedules. A young dog’s heat season might be irregular at first and take up to two years to transition to a regular cycle.


Getting your female dog spayed can prevent their heat cycle. If any lingering symptoms of heat occur in a spayed pup, consult your vet.

For fertile dogs who are still able to get pregnant, do your best to keep your dog comfortable during her heat cycle by distracting her with engaging activities or encouraging her to rest if she is lethargic. Never allow her outside without you or off-leash. Male dogs are drawn toward females in heat and unwanted situations can ensue if proper care isn’t taken.

Be understanding if your dog behaves strangely toward you, even aggressively, during her cycle. Other behaviors like mounting soft objects might occur, and should be ignored whenever possible. You can even provide your dog with soft toys around their own size if they persist in the mounting behavior.

Keep your dog off of things that can be stained by blood and other bodily fluids and consider using doggy diapers for the duration of the first 2 stages of heat.

If you are planning on letting your dog get pregnant, do as much research as possible to make sure your family is really ready.

Three Chinese Crested Puppies, including two hairless Chinese Crested puppies and one Powderpuff Chinese Crested Puppy.
Chinese Crested Dog Puppies