What to Know About Dogs in Heat

All advice given is general in nature. If you have any immediate or specific concerns, please talk to your vet.


Knowing the signs that your dog is in heat is important for both male and female dog parents, as it’s crucial for avoiding unwanted pregnancies and for planning for puppies when you do want them. While it only happens to bitches (female dogs), owners of unneutered male dogs will also need to be cautious.

What does 'in heat' mean?

Going into heat is a bitch’s way of indicating that she’s entered the fertile period of her reproductive cycle, where she can get pregnant. This stage is also known as the ‘estrus’ stage.

When does a dog’s heat cycle start?

A bitch’s heat cycle starts when she reaches sexual maturity. She’ll usually go through heat for the first time at around 6 months old, but this age can vary and can be as late as two years old in large and giant breeds.

How often do dogs go into heat?

Your dog will continue to go into heat approximately every 6-8 months for the rest of her life. Again, this can vary between breeds, with very small dogs often going into heat three or four times a year and giant breeds experiencing it just once a year.

For most bitches, their reproductive cycle gets longer as they get older, but unlike humans, they will never go through menopause. If she’s spayed, however, her seasons will stop, and she will no longer be able to get pregnant. If your dog is not spayed and misses heat, contact your vet.

How long are dogs in heat for?

The fertile window in your dog’s heat cycle can last between two and four weeks, averaging at three weeks. Some bitches will have a slightly longer or shorter heat, but they generally should become quite regular once they reach 18 months old.

Signs your dog is in heat

Some of the signs your dog is in heat are more obvious than others, and these signs will vary from dog to dog. The more aware you are of your dog’s cycle, the more you’ll be prepared to handle any changes in her behaviour, as well as physical symptoms such as bleeding.

Male attention

One of the first things you might notice when your dog enters heat is that she’s attracting unneutered males from far and wide. Later into her cycle she may even seek out the males herself. Mounting other dogs or objects is also a common behaviour of dogs in heat.

Tail position

When your dog is in the early stages of heat, you may notice her holding her tail between her legs. She will do this to protect herself from male advances. But as her cycle progresses, she will likely begin to hold her tail to the side, which lets males know she is ready for mating.

Changes in behaviour

Your dog can become a bit agitated or nervous during heat, so be aware that she may show increased aggressive behaviour towards other pets or even people. On the other hand, she may become clingier or more affectionate towards you.

Increased urination

An increase in urination during heat is common, as it’s used as a method of alerting male dogs in the area that she is open to mating.

Bleeding and swelling

When she goes into heat, her vulva may become swollen and more pronounced. There will also be a bloody discharge, which may leave spotting on her bedding or around your home. This usually only lasts for around 7-10 days of her cycle but will likely become bloodier in appearance towards the end of this period.

The Estrus Cycle

The Estrus Cycle is the technical term for a bitch’s heat cycle. This can be broken down into four key stages. After reaching sexual maturity, she will always be in one of these stages.

1. Proestrus stage

The first stage of the cycle is called proestrus, which lasts between three and 19 days. This is the phase when your dog is preparing to mate and symptoms will begin, such as a swollen vulva and bloody discharge. She’s not ready for mating yet, so may hold her tail between her legs or sit down around male dogs.

2. Estrus Stage

The Estrus stage is the mating phase when your dog is at her most fertile. It generally lasts around nine days but can be as short as three days or as long as 21. During this time, you might observe that your dog is actively ‘courting’ males by behaving in an overly friendly way and presenting herself with her tail to one side.

3. Diestrus Stage

In this stage, your dog’s fertile period has come to an end so her body will either return to normal, or she will develop a pregnancy. Symptoms such as swelling and discharge will subside, and she will no longer be interested in male advances.

4. Anestrus Stage

Anestrus, or also known as the “resting” stage, is the last stage of the cycle. If she’s not pregnant, she will remain in this stage until her cycle begins again. Alternatively, she will enter this stage after giving birth.

Dogs can go into heat again as early as two weeks after giving birth, but generally it will happen between four to six months later.

How to care for your dog in heat

Being a responsible dog parent during this time is as much about helping her feel at ease, as it is about taking the necessary precautions to avoid an unwanted pregnancy.

Provide comfort and love

Your dog may feel a bit sensitive or out of sorts during heat - especially her first one, so do everything you can to make her feel comfortable and loved. Pay attention to any behaviour changes and give her the space or attention she needs.

Practise good hygiene

It’s important to change her bedding regularly to prevent bacteria growing and have supplies on hand to clean up after accidents caused by increased urination and spotting. Some dog parents use doggy diapers to avoid causing a mess, but make sure you’re changing them frequently if you do.

Avoid contact with other dogs

You’ll need to be very careful while your dog is in heat. Don’t leave her unattended with other dogs. If they’re unneutered it could lead to an unwanted pregnancy, and even if they’re female or neutered, it can trigger uncharacteristically aggressive behaviour.

Always walk your dog on the leash as her hormonal drive to find a male may override her recall ability. It’s also wise to walk her at quieter times when there are less dogs around.

Caring for a dog in heat can take patience and love, but with the right attention it can easily be managed. By learning what signs to look out for, you can be prepared for what’s to come. For further advice on caring for your dog, take a look at our Petcare Blog.


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