The four stages of a dogs heat cycle, explained

18 September 2023 - 6 min read
lurcher cross tan colored dog gtting hair blown out with pink hair dryer on blurred out background

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 behavioural 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.

A person high fiving a dog

Get £15,000 lifetime vet fee cover with our Complete policy.

A person high fiving a dog

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 behavioural 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 behaviour.

2. Estrus (fertile territory)

Estrus, not to be confused with “estrous” in “estrous cycle”, is the centrepiece 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 behaviour.

Not surprisingly, your pup’s behaviour 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 lead 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 behaviours.

For instance, you might notice your dog engaging in "phantom pregnancy" symptoms. These can range from mild nesting behaviour 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 normalise.

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 normalised 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.


Top-quality dog insurance

We've got your dog's back.

Nose-to-tail dog insurance for accidents and illnesses at competitive prices with no hidden fees.


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 mum to the vet. They'll offer personalised 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 cosy 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 family permanently, you have some options:

  • Adoption: The classic choice. There are countless loving homes looking to adopt a puppy. If you go this route, socialise 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 organisations: You can try approaching rehoming centres or charities such as the Dog's Trust or Blue Cross who may be able to help. You can also find rescue centres via the Association of Cats and Dogs Homes.

  • 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.

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 it. 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 behaviours. 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 organisations only have so much space and can be under a lot of pressure. If you can avoid adding to that pressure through responsible pet ownership, it can only be a good thing.

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 cover those unexpected vet bills, even when vet costs get out of paw.

A cat with its arm on a woman, they are looking at each other

All our policies cover conditions that ended at least two years ago.

A cat with its arm on a woman, they are looking at each other