How Often Do Dogs Go Into Heat?

Dr. Jason Gagné, DVM, DACVIM
By Dr. Jason Gagné, DVM, DACVIM
Updated: 5/6/20242-4 minutes
person hugging brown and white dog

From the age of around 6 months, a female dog will start experiencing heat cycles, or ‘coming into season’.  You may notice changes in your four-legged friend that will signify that they are in heat. 

Learn all about your dog’s heat cycle, how long it lasts and what to look out for.

What is a Dog Heat Cycle?

A dog heat cycle lasts about six months, and at certain points in this cycle, termed being ‘in season’ or ‘on heat’, your female dog is fertile and can become pregnant. During this time your dog will bleed from their vulva and will often show more interest in male dogs. 

When Does a Dog’s Heat Cycle Start?

Some bitches can start their heat cycles as early as four months, however, this is unusual and is most common in smaller dog breeds. Larger dog breeds tend to start their heat cycles at around 8 to 12 months. The average among all breeds is around nine months. 

It is advised that young female dogs should not be bred during their first two cycles, as they are not yet fully mature themselves. To make sure you are breeding your dog at the right time, you should seek the advice of your vet and they will be able to tell you when your dog is mature enough to start breeding.

How Often Does a Dog Go Into Heat?

After your dog’s first heat cycle, your dog will experience their next one every 6-7 months on average. This means a dog will be in heat twice a year. When your dog starts to mature in age, their cycles may become less regular. However, if you have a young dog and their cycles are irregular, or you have any other concerns you should contact your vet.

If you have a dog that’s been spayed, they will not experience a heat cycle.

How Long is a Dog in Heat?

A dog will usually be in heat for anywhere between 2 to 4 weeks, and they are usually most fertile around day 10. Within the first few days of a heat, they may not be responsive to male dogs. While this is normal for some, others may be much more interested in male dogs from the beginning of their cycle.

It is important to note that during heat, your dog may not bleed the entire time. 

Some dog heat cycles will be shorter than others, and it can be tricky to tell when your dog’s heat has finished. You can look for clues as to when the heat has finished such as the size of their vulva, which will return to its normal size and there will be no bleeding.

Signs of a Dog Heat Cycle

There are a few signs that your dog will show at the beginning and during their heat cycle. These signs will settle down at the end of their heat which will usually indicate that it has finished.

  • Red, swollen vulva  
  • Bleeding or discharge from the vulva  
  • Excessive licking of the back end  
  • Urinating more than usual

You may also notice behavioral changes in your female dog when they are in heat. These changes may be a sudden over-friendliness towards other dogs, mounting or humping objects, heightened anxiety and moving their tail to one side when standing.

When is My Dog Most Fertile During Their Cycle?

During your dog’s heat cycle, there is a small window of fertility. This window can start anywhere from 9 to 10 days after she goes into heat. This window of fertility will last for about 5 days. There is no hard and fast rule though, and your dog can fall pregnant at any time during heat.

How to Care for Your Dog When They Are in Heat?

There are a few things you can do to keep your dog comfortable while they are in heat.

  • Keep them entertained – offer them their favorite toy or give them a new puzzle toy to keep their minds distracted 
  • Keep their beds clean and comfortable  
  • Make sure you keep an eye on their cleanliness – if they are bleeding heavily, bathing your dog will be the best way to keep them nice and clean 
  • If bleeding is heavier than normal, or your dog is showing signs of illness, you should seek veterinary advice as soon as possible - it may be a sign of pyometra, a type of womb infection 
  • Offer them plenty of water and keep an eye on their appetite too

While there is no pain felt during a dog’s heat cycle, they will still appreciate being made to feel comfortable during this period of time.

Keeping an eye on your dog’s overall behavior and body language during their cycle will indicate whether they need extra support or not during this time. Despite these cycles only happening twice a year, it is important that you note whether they are regular or not. If you think there is any cause for concern during your dog’s heat cycle, seek advice from your vet. 

Remember that having your dog spayed is the best option for most female dogs. 

For more expert tips on dog health, explore our other dog health articles. 

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