What Are The Stages Of Dog Heat?

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Dogs in heat are ready to reproduce because they’re ovulating, which means they’re fertile and can become pregnant. As a result, dogs in heat may experience changes in their behavior to show they’re open to mating. This is when they could become pregnant if they meet an intact male dog, so you may need to keep her away from other dogs during this time to prevent unwanted pregnancy. 

There are multiple stages of dog heat, and understanding the cycle is key to ensuring your dog does not become pregnant if you don’t want them to. If you want to breed your dog, it’s also equally important to know when they’re fertile when you introduce them to a mate. This article will discuss the dog heat cycle stages to help you make the best decision for your dog. 

When Do Female Dogs Go Into Heat?

Female dogs can go into heat as early as four months old. However, large dogs may not enter their heat cycle until they reach 18 to 24 months.1 However, their eggs are not fully mature when dogs are young, so they may not experience a healthy pregnancy. Ultimately, just because your dog can become pregnant doesn’t mean they should when they’re still young. 

On average, the first heat for dogs begins around six months of age,1 but it depends on the breed. If you’re trying to prevent pregnancy in your dog, there are many signs to look for to determine whether your dog has reached puberty yet. 

After a dog has started their first heat, they can breed anytime during heat, and the heat cycle occurs about every six months. However, the frequency may differ by breed. For example, small dogs go into heat more frequently than larger breeds.2 Therefore, a Yorkshire Terrier might go into heat three or four times per year, while a Pitbull only goes into heat once yearly.

After reaching puberty, dogs go into heat throughout the rest of their lives, although the cycle changes as they get older.2

Signs That Your Dog Is In Heat

During the heat cycle, your dog’s behavior may change. For example, many dogs actively seek out males to become pregnant, so your dog may appear more energetic or hyper than usual. Signs your dog is in heat include:

  • Vaginal bleeding: Dogs start their heat cycle by bleeding, so you may notice red or brown discharge around their genitals. This bleeding typically occurs for 7 to 10 days.1 Learn more about how long periods last
  • Licking themselves: During the first part of the heat cycle, your dog’s vulva will swell and produce a bloody discharge. Since dogs like to clean themselves, you may notice your dog licking more than usual. 
  • Seeking out males: Dogs in the heat cycle tend to look for mates, so they may become more friendly with male dogs at the park or on walks. During this time, males will also show more interest in your dog than usual. 
  • Changes in urination: Dogs in heat may urinate more often than usual, indicating that your dog is in heat. Additionally, urinating in front of male dogs or lifting their legs in front of males may indicate they're ready to mate. Of course, changes in urination habits could also indicate a dog’s urinary health issue, so if your dog hasn’t started their cycle yet, take them to the vet to ensure they don’t have a urinary tract infection or another health issue that causes frequent urination. 
  • Mounting and humping: Female dogs may mount or hump as a sign they’re ready to mate. Dogs in heat may hump female or male dogs or other items like pillows around the house. 
  • Nervousness: Female dogs in heat may become irritable or anxious. They may also begin nesting or preparing a safe spot to have puppies even before she becomes pregnant. 

What Are The Four Stages Of A Dog In Heat?

The four stages of heat for dogs

Dogs in heat have four stages, and there are signs to each one of them to help you understand where your dog is in her cycle. The four stages of dog in heat are:

1. Proestrus Stage

The first stage of a female dog’s heat cycle is the proestrus stage, which lasts from 7 to 10 days.1 In this stage, the vulva swells, so your dog may lick herself more often. She may also become more or less affectionate, so there will be noticeable changes in her behavior. Female dogs in the Proestrus stage may also tuck their tails to guard their vulvas around other animals because they’re not yet ready to mate. 

2. Estrus Stage

During the estrus stage, which lasts between 5 and 10 days,1 dogs are fertile, meaning the ovaries have started releasing eggs. Since the eggs are ready for fertilization, female dogs will try to spend more time with male dogs, maybe approaching them at the park or on walks. She will also move her tail from a tucked position off to the side to show off her fertility to males that might be interested in mating. 

Her vulva is less swollen during the estrus stage to allow easy mating. She may also flirt with other dogs and turn her rear to them to show them she wants to mate. 

3. Diestrus Stage

The diestrus stage lasts from 10 days,depending on the dog’s breed, and signals the end of the heat cycle. Once the dog has reached this stage, they’re no longer fertile, so they may be less accepting of male company. However, if your dog is pregnant, they will stay in this part of the cycle until the puppies are born. 

4. Anestrus Stage

During the anestrus stage, dogs are no longer fertile, and their bodies and behaviors go back to normal. For example, a once flirtatious dog will no longer actively seek out male attention. The anestrus stage can last up to six months, depending on the dog and whether or not they’re pregnant. At the end of this stage, the heat cycle begins again with the first stage, proestrus. 

How To Care For A Dog In Heat

Tips for caring for a dog in heat

Caring for a dog in heat requires you to take special consideration of the different cycles they go through. For example, some dogs in heat may become more affectionate while others become aggressive, so you’ll have to care for them based on their behavioral changes. Here are a few ways you can care for your dog when they’re in heat: 

  • Don’t leave them alone: If you’re trying to avoid pregnancy, never leave your dog unattended, even if it's in your own yard. Dogs in heat are more likely to run away to find a mate, which could put your dog in danger. Instead, watch your dog in your yard or hook them up to a leash to prevent them from leaving your sight. 
  • Keep them on a leash: Dogs who are normally well behaved off leash at the park or on walks should be kept on a leash while they’re in heat because their natural instincts are telling them to seek out a mate. If you want to avoid pregnancy and prevent your dog from running away, keep them on a leash at all times during their cycle. 
  • Use diapers: Female dogs bleed when they’re preparing for ovulation, which can be messy. You can protect your furniture and carpet and prevent your dog from licking themselves by putting them in doggie diapers while they’re bleeding. 
  • Make them comfortable: Dogs may act differently when they’re in heat. Some will be energetic while others will be tired or even depressed. You can make your dog more comfortable by giving them blankets and an adequate amount of exercise and space if needed.
  • Consider sterilization: If you don't want your dog to get pregnant, the best thing you can do for her is have her spayed. This will prevent her from entering the heat cycle and allow her to enjoy a healthy life without ever getting pregnant. 

Dog mom laying on grass with her puppies nursing

Next steps

All female dogs that haven’t been sterilized will enter the heat cycle eventually, but how long it takes your dog to become fertile depends on their breed and size. Once your dog reaches puberty, you must learn how to care for them based on their needs and where they are in the cycle. Since female dogs will act differently when they’re fertile, it’s always best to keep an eye on them to prevent them from searching for a mate. 

Female dogs experience behavioral changes running from becoming more affectionate to aggressive and even anxious. If your dog is experiencing anxiety during her cycle, you can help her feel better by talking to a Dutch vet. Dutch vets are here to answer your questions about your dog’s heat cycle and how you can make her more comfortable with dog anxiety treatment and by keeping her away from males. If your dog becomes pregnant, we can help you learn how to care for your pregnant dog and her puppies once they’re born. 



  1. “Dog in Heat (Canine Estrus): Symptoms and Spaying.” WebMD, Fetch, https://pets.webmd.com/dogs/how-tell-if-dogs-heat.

  2. “How Often Do Dogs Go into Heat.” American Kennel Club, American Kennel Club, 14 Mar. 2018, https://www.akc.org/expert-advice/dog-breeding/when-dogs-in-heat/.

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