The four stages of a dog's heat cycle, explained

September 19, 2023 - 6 min read
This article is not intended to be a substitute for professional veterinary advice, diagnosis, or treatment. Always seek the advice of your veterinarian with any questions you may have regarding your pet’s care, treatment, or medical conditions.
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When we talk about the canine “season cycle,” we’re not talking about the weather; we’re talking about the female reproductive cycle, also known as the “estrous cycle” or the “heat cycle.”

Knowing the ins and outs of your dog’s season cycle can help you prevent an unwanted pregnancy. Just as importantly, it can let you anticipate certain behavioral shifts and help you provide the care your pet needs as she transitions between the different phases of the cycle.

There are four phases, by the way: Proestrus, Estrus, Diestrus, and Anestrus.

Four Stages of a Dog's Heat Cycle

1. Proestrus (The Prologue)

Proestrus is when a female dog’s body starts to prepare for the possibility of pregnancy. Hormone levels begin to shift, and her ovaries start to mature eggs. You'll likely notice some physical signs, too, like bleeding. (As with menstruation in humans, this is a natural bodily process and nothing to be alarmed about.) Don’t be surprised to see male dogs in the vicinity starting to gather around her, though she won’t be willing to mate during this phase.

You'll likely notice behavioral changes, too. She may become more clingy or affectionate with you, or conversely, she might become a tad more irritable or anxious. Each dog is different, and these shifts can vary widely.

The timeline of proestrus varies from dog to dog. While some might breeze through it in a swift three days, others could stretch it out for as long as 17 days. However, the majority of dogs average around 9 days.

It’s a good idea to keep an eye on your dog’s diet and exercise during proestrus. Hormonal changes can affect her appetite and energy levels. Some dogs may eat less or seem less interested in physical activity, while others may exhibit the opposite behavior.

2. Estrus (Fertile Territory)

Estrus (not to be confused with “estrous” in “estrous cycle”) is the centerpiece of the canine reproductive cycle, when your dog is fertile and capable of conceiving puppies. Estrus can last anywhere from three to 21 days, though the average falls somewhere in-between. 

During estrus, your dog’s estrogen levels drop, and her progesterone levels begin to rise. These hormonal changes prepare her body for possible pregnancy. While you won't be able to see these internal adjustments, they profoundly influence her receptiveness to male dogs and her overall behavior.

Not surprisingly, your pup’s behavior toward male dogs may seem more playful or affectionate during estrous. If puppies aren't in your plans, now’s the time to be extra vigilant. Keep her on a leash during walks, and carefully supervise any interaction with male dogs.

If you have no intention of breeding your dog, you might want to consider scheduling her spay surgery as soon as possible. (More on this later.) 

Nutrition is also crucial during this period. Since your dog’s body is going through a lot, you'll want to make sure she's eating a balanced diet rich in the nutrients she needs. Again, don't be surprised if her appetite changes—hormonal fluctuations can do that. Keep her well fed, but avoid overfeeding; excessive weight can lead to complications, whether she becomes pregnant or not.

Finally, remember not to neglect exercise. While you may have to adjust your walking routes or avoid the dog park to prevent unwanted attention, she still needs her daily dose of physical activity. 

3. Diestrus (Calming Down)

Think of this as the cool-down phase after estrus.

Diestrus can last anywhere from two to three months. Hormone levels will taper off and eventually return to their baseline. If you've been on high alert during estrus to avoid an unwanted pregnancy, you can finally let your guard down a bit.

Now here's the peculiar part: Whether or not your dog has mated and become pregnant, her body essentially behaves as if she's expecting. No matter what, she'll be producing hormones like progesterone to support a possible pregnancy. This hormonal shift can result in some fascinating and, at times, confusing behaviors.

For instance, you might notice your dog engaging in "phantom pregnancy" symptoms. These can range from mild nesting behavior to more advanced symptoms like milk production. Rest assured, this is generally considered normal unless it’s causing them stress or medical issues.

Diestrus is also an important time for bodily healing. You should notice any bleeding or discharge start to disappear, and your pup’s mood and energy levels will start to normalize.

As always, maintain a balanced diet and exercise. This is especially important if your dog has mated and there’s a chance she’s become pregnant.

4. Anestrus (Time Off)

So you've weathered the storms of proestrus, estrus, and diestrus. Say hello to anestrus, the dormant phase of your dog's reproductive cycle. Anestrus lasts around four to five months, offering a breather for both you and your pup. No more male admirers lurking around, and no more watching your dog like a hawk during walks.

Estrogen and progesterone levels will have both normalized at this point, and your dog will likely be less prone to mood swings or irritability. This is a fantastic time to focus on your pup’s general well-being.

Even If your dog became a fussy eater during earlier phases in her heat cycle, she may get back to her regular eating habits during anestrus. Remember, a balanced diet is essential year-round, not just during the reproductive phases. Physical activity should also remain consistent.

With hormones at a steady level, it's also a good time to schedule any elective surgeries or procedures, like spaying. The risks associated with these surgeries can often decrease during anestrus.

Handling Unplanned Pregnancies in Dogs

Breeding your dog should always be a well-thought-out process, not an accident. Nonetheless, accidents do happen. If your fur baby is expecting some fur babies of her own, it’s time to take some important steps.

Start by taking your expectant dog mom to the vet. They'll offer personalized advice and help you make sure your dog is healthy and ready for motherhood. Meanwhile, provide your dog a balanced diet and just the right amount of exercise so both she and her future puppies are in tip-top shape.

As the due date approaches, make a cozy space for the big arrival. And be sure to schedule postpartum check-ups for the proud mom and her new puppies.

If you’re not planning on expanding your fur fam permanently, you have some options:

  • Adoption: The classic choice. There are countless loving homes looking to adopt a puppy. If you go this route, socialize the puppies well and make sure they're up-to-date on their vaccines and vet checkups before they go to their new homes.

  • Rescue Organizations: Some groups specialize in specific breeds and are always on the lookout for new pups to rehome.

  • Friends and Family: Sometimes the perfect home is closer than you think. Your extended network might just contain the perfect pet parents, saving you the search.

  • Foster-to-Adopt Programs: These initiatives allow potential adopters to test-drive life with a new pet, making sure they’re the right fit before adopting them for good.

To Spay or Not to Spay

Choosing whether or not to spay a female dog is ultimately a personal decision.

If you’re planning to breed your dog, the decision is a pretty simple one! But if you’re not, you should seriously consider spaying your pup. The vast majority of vets recommend it (though the right time to do it may vary by breed).

Spaying carries a number of health benefits for female dogs, including a reduced risk of mammary, uterine, and ovarian cancers, as well as a diminished risk of the life-threatening uterine infection pyometra. One study found that spayed dogs live about 26% longer than dogs who aren’t spayed!

Worried about your dog changing after a spay? Many of these could be positive. When you eliminate the intense hormonal fluctuations caused by your dog’s heat cycle, you’re also likely to eliminate some unwanted behaviors. Spaying your dog can reduce or eradicate things like marking, howling, excessive barking, or even running away in search of a mate.

Finally, keep in mind that rescue organizations only have so much bandwidth to take care of cast-off pups. Spaying your pet can play a major role in reducing the number of euthanized dogs.

ManyPets Has You Covered

Your dog's season cycle comes with plenty of potential health risks, from infections to cancer. ManyPets dog insurance can help keep you financially protected, even when vet costs get out of paw.


David Teich
Lead Content Editor

David Teich is Lead Content Editor at ManyPets. He loves pets, Scrabble, Oxford commas, and typing loudly.