Get

In Your Inbox

Dogster is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Physical Signs of Proestrus and Estrus in Dogs: Vet-Reviewed Info & FAQ

Share

male and female Eurasier dogs

Whether you want to breed your female dog or are anxious to get her spayed before she undergoes her first heat cycle, knowing the physical signs indicating the start of the heat process is essential. The canine reproductive cycle is divided into four parts: proestrus, estrus, diestrus, and anestrus. Proestrus and estrus are the two parts that occur when the dog is considered to be “in heat”.

The main physical signs of starting proestrus are swelling of the dog’s vulva and bloody discharge. The main physical signs that the dog has progressed into estrus include a wrinkled vulva, caused by a rapid decrease in swelling, and the discharge becoming watery or lighter in color.

divider dog paws 2 oct 2024

Important Considerations

There are no benefits in having your dog experience multiple heat cycles throughout her life if you don’t intend on her having puppies. Spaying female dogs is strongly recommended as it will prevent pet overpopulation on a large scale and will protect your dog against several health issues that they may otherwise be at high risk of developing, such as mammary tumors and pyometra; an infected uterus that may lead to sepsis and kidney damage.

Dogs that don’t get a clean bill of health shouldn’t be bred, as the resulting litter may have unhealthy puppies, which leads to deteriorating breed health and welfare issues.

Animal shelters are overpopulated and overwhelmed with abandoned and unwanted dogs, many of which get put to sleep or spend their whole life in a small cage, not being able to express their normal behavior or have a fulfilled life. By breeding dogs, we may contribute to this issue of pet overpopulation. Before breeding your dog, consider this crucial ethical aspect, as adopting another dog or a puppy may bring equal joy to your home, and you will make a life-changing difference to that poor pooch.

What Happens During Proestrus and Estrus?

Proestrus and estrus occur when your female dog’s body is preparing for possible breeding and pregnancy. Most dogs will go into heat about every 6 months, although there is some size and breed variation. Female puppies usually experience their first heat around 6 months of age, but it can happen anywhere between 4 and 24 months, depending on their breed and size. Besides the physical signs already mentioned, most dogs will undergo some behavioral changes during proestrus and estrus.

Proestrus

a female dog is cleaning the genitals by licking
Image Credit: SOORACHET KHEAWHOM, Shutterstock

Proestrus is the first stage of the dog’s heat cycle. In the days leading up to the start of proestrus, you may notice your dog seems nervous, more tired than usual, or maybe she is eating less. Proestrus starts when her vulva swells up and a bloody discharge begins. Around this time, you may also start to notice male dogs taking an interest in your female. She will most likely first be aggressive and then indifferent to male dogs as she progresses further into her proestrus. Proestrus usually lasts around 9 days, but the length can be anywhere from 3 to 17 days.

Estrus

Estrus is the stage of the cycle when your female is ready and usually willing to breed. You will notice that your dog’s vulva becomes smaller, softer, and wrinkled as she moves into estrus. Her discharge will become less bloody. Behaviorally, you may notice that she is now interested in male dogs rather than aggressive towards them. She may carry her tail up or to the side, a behavior known as flagging. Estrus can last from 3 to 18 days, with around 9 days being the average.

What About the Other Phases of the Reproductive Cycle?

Dog Heat Cycle
You are free to use this image but we do require you to link back to Dogster.com for credit

The two final phases of a dog’s reproductive cycle are diestrus and anestrus.

Diestrus occurs after estrus and usually lasts about 2 months. During this stage, your dog’s hormone levels are changing. You will likely not notice any physical changes in your dog unless she has become pregnant.

Anestrus is the final phase of the cycle, which usually lasts around 4 months, but can be longer. During this phase, your dog will not exhibit any physical signs but internally her body is preparing for the start of the next proestrus.

Your Dog Is in Heat: Now What?

dog sniffing ready to mate
Image Credit: High Simple, Shutterstock

You’ve learned what the physical signs of proestrus and estrus are and, sure enough, now you’ve noticed them in your dog. What should you do?

If you are not planning to breed your dog, make sure no unneutered male dogs can get near her during estrus. This includes any male dogs that are related to her.

Keep your female leashed during walks and only let her out into a fenced area without any other dogs. You will still need to supervise her when she’s outside. Male dogs are notoriously persistent in the presence of a female in heat so be sure to be extremely vigilant to prevent accidental breeding.

If a male dog does get to your female despite your watchfulness, contact a veterinarian to learn what your options are to prevent pregnancy.

Did you know you can speak to a veterinarian without having to travel? Just head over to PangoVet. It's our online service where you can talk to a vet online and get the advice you need for your pet — all at an affordable price!

PangoVet_Mention-in-Content Savings V1

Proestrus and estrus can cause quite a mess due to the bloody discharge. To try and contain the mess, you may choose to keep your dog in a crate or easy to clean room while she’s in heat. If she tolerates it, you can also have your dog wear a dog diaper during her proestrus and estrus. Dog wipes can be useful in keeping your dog clean as well.

If you plan to breed your dog, make sure you thoroughly research everything that goes into being responsible before you commit to the process. Responsible dog breeding is a time-consuming and often expensive undertaking. Pet overpopulation, which leads to unwanted and abandoned pets in crowded and overwhelmed dog shelters, is a huge concern, so make sure you are breeding your dog for the right reasons and that you do it properly.

You Don’t Want to Deal With a Dog in Heat: Now What?

dog anesthesia with veterinary treatment
Image Credit: thirawatana phaisalratana, Shutterstock

If you don’t want to breed your dog and you think that dealing with a dog in heat sounds like a hassle, the best thing to do is have your dog spayed, or “fixed”. Besides being more convenient, there are several other reasons it’s a good idea to spay your dog.

Spaying your dog before she first goes into heat will almost eliminate the chance that she will get mammary (breast) cancer later in life. This type of cancer can be painful and hard to treat so avoiding it altogether is the best way to go.

Unspayed female dogs can also develop a serious infection in their uterus called pyometra. Pyometra can make your dog very sick and will kill her if not treated. Spaying your dog will keep her from developing this life-threatening condition.

As already mentioned, pet overpopulation is a serious issue in many parts of the world. By spaying your dog, you make certain that she won’t be contributing to that problem. Spaying your dog is not only beneficial for her and convenient for you but helps make a difference in the lives of homeless dogs as well.

If you are ready to spay your dog, a veterinarian will be able to give you more information on the process and what to expect as your dog recovers.

divider dog paws 2 oct 2024

Conclusion

Knowing the physical signs of proestrus and estrus will help you be aware of when your dog’s heat cycle begins. This knowledge will help you prepare to manage your dog during her heat period. Of course, you want your dog to be as safe, clean, and comfortable as possible while she experiences this process. Educating yourself is an important part of being a responsible pet parent and you’re doing your part!


Featured Image Credit: JackieLou DL, Pixabay

Want content like this delivered to you?

Sign Up For Our Newsletter

News, insights, expert advice, and everything dog

* By submitting, you agree to our Terms & Conditions and Privacy & Cookies Policy.




How useful was this post?

Click on a star to rate (you can leave written feedback after clicking submit)

Help us improve Dogster for pet parents!

Your feedback really matters.

What did you like about this post? Also how can we improve it?

Join the conversation

Leave a Reply

You’re very welcome to leave a comment or question. Please know that all comments must meet our community guidelines, and your email address will NOT be published. Let’s have a positive and constructive conversation.


Talk With A Vet Online

Peace of mind,
anywhere, anytime

Affordable vet advice

Ask Dr. Paola- Help! My Dog’s Sleeping Habits Have Changed! (May 18, 2026)

Welcome to our “Ask Dr. Paola” series, where every Monday we bring expert advice straight from Dr. Paola Cuevas (MVZ) to help our...

The Crate Setup Most Dog Owners Get Wrong (And How To Fix It!)

Most people assume that if their dog hates the crate, the crate is the problem. So they try a bigger one, a different...

1,500 Beagles Rescued from Wisconsin Lab Farm – Here’s Where They’re Going

You may remember that a few weeks ago, we reported on a tense situation at Ridglan Farms, Wisconsin, a facility infamous for housing...

Dogster’s Weekly Photo Contest Winners: Window Watchers (May 11, 2026)

Every week our team gets the privilege of sorting through our readers photos to choose what dogs will win this weeks contest! See...

More related

How Much Do Dog & Puppy Vaccinations Cost? 2026 Price Guide

You want your pet to be as healthy as possible and remain that way throughout their life. Part of basic healthcare for your...

National Dog Biscuit Day 2026: What It Is & Ways to Celebrate

Did you know there is a whole day of the year devoted just to doggie biscuits? Well, mark your calendars, because every February...

The Art of Nicknaming Your Dog: Tales from the Wednesday Dogs of Dogster (with Video)

Welcome to the Wednesday Dogs of Dogster! Every month, we ask our Dogsters to weigh in on a new topic. This week, we...

8 Common Dog Paw Problems & What to Do (Vet Answer)

Issues with your dog’s paw(s) can occur for a number of reasons. Dogs can suffer wounds, issues with their nails, or cause trauma...

Keep reading

10 Best Bowls for Small Dogs in 2026 – Reviews & Top Picks

Finding the perfect bowl for a small dog will be different for every owner because, apart from their size, every small dog differs from the next. We can all agree that some of our needs overlap; the perfect bowl is...

French bulldog eating from a bowl

Hill’s Science Diet Puppy Food Review 2026: Recalls, Pros & Cons

Review Summary If you’ve got a growing pup, you know how important it is to give them the best fuel possible. Hill’s Science Diet puppy foods are a great choice because of the company’s research-backed approach to nutrition. With over...

Dogster_Hill’s Science Diet Puppy Food Review

Can Dogs Eat Rye Bread? Vet-Verified Nutrition Facts & FAQ

Sharing food comes naturally to us. It doesn’t matter if it’s our family or a friend; it’s a bonding experience. Therefore, it’s not a stretch if the things we want to give our dog extends to many tasty morsels we...

Can Dogs Eat Rye Bread

Can Dogs Eat Tomatoes? Health & Nutrition Facts

Whether eaten raw or cooked in a delicious sauce, tomatoes are a staple of many human diets. If you’re tempted to slip your dog a slice, you’ll first want to determine whether dogs can safely eat tomatoes. Ripe tomatoes are...

Can Dogs Eat Tomatoes

Can Dogs Eat Rutabagas? Vet-Reviewed Facts & FAQ

As a pet parent, you want to ensure your dog is healthy and happy. It’s well known that dogs can eat a variety of vegetables like carrots, spinach, peas, and even fruits like apples and blueberries. And you’ll even find...

Can Dogs Eat_Rutabagas

Can Dogs Eat Parmesan Cheese? Vet-Verified Facts, Risks & FAQ

If you’re a dog owner, you’ve probably found yourself sharing a snack with your furry friend at some point. Dogs can be notorious beggars when it comes to food, and it’s hard to resist those pleading eyes. For cheese lovers,...

Can Dogs Eat_parmesan cheese

Can Dogs Eat Alfalfa? Vet-Verified Facts to Know

Alfalfa is an important grazing plant that feeds livestock worldwide. Many people wonder, can dogs can eat alfalfa? The short answer is yes, alfalfa is a healthy food for dogs. However, there are a few factors to consider before making...

Can Dogs Eat Alfalfa

Canidae Dog Food Review 2026: Recalls, Pros & Cons

Review Summary   Aimed at dogs of all shapes, sizes, and ages, Canidae dog food has been around since 1996 and is one of many high-quality brands available for pets throughout the U.S.A. With its focus on sustainable and regenerative...

Dogster_Canidae Dog Food Review

Love Dogs? So Do We! Join the Dogster Community

Stay informed with expert pet care insights delivered straight to your inbox! Discover professional guidance on animal behavior, feeding tips, trusted product picks, and much more.




Sign up for the Dogster Email Newsletter