How Long Are Dogs in Heat?
Here’s what you should know about the dog heat cycle—and what to expect if your pup isn't spayed.
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If your sweet little girl isn't spayed, don't be caught off guard if she gets her period. This is the beginning of her estrus cycle, commonly called "heat." During heat, a female dog is open to mating and can become pregnant. And while bleeding is one of the most obvious signs a dog is entering heat, her estrus cycle actually lasts much longer than this initial stage.
So, how long are dogs in heat, exactly? And how do you know when your dog is ready to mate? Daily Paws spoke with a veterinarian to find answers.
When Do Dogs Go Into Heat?
This time of fertility and breeding can be a fact of life for your dog at a surprisingly young age. Lonna J. Nielsen, DVM, of Winterset Veterinary Center in Winterset, Iowa, says, "The timing of the first heat varies by the size of the dog. It can be as soon as 6 months of age for small dogs or 1.5 years for giant breeds. Having an intact [non-neutered] male in the house will bring heat in faster for a female. It can be as young as 4 months [old] for small dogs!"
The Female Dog Heat Cycle
how long are dogs in heat infographic showing the four stages
Just how long are dogs in heat? You might be surprised to find out that your dog's heat cycle can last weeks, and "it is a full 30 days that the female should be confined and not outside alone," Nielsen says.
Stage 1: Signs a Dog Is in Heat
The first signs your dog is in heat are the swelling of her vulva and bright red bloody discharge. This stage is called proestrus. "There will be lots of licking," Nielsen says. A dog in heat can bleed for around seven to 10 days. During this first stage of the reproductive cycle, the female will not accept a male.
Stage 2: When Your Dog Can Become Pregnant
Once the bleeding stops, the second stage of the dog heat cycle, called the estrus stage, has begun. Many people make the mistake of thinking their dog's estrus is done at this point, but this second stage is actually when your dog can become pregnant. "This stage, when the blood is done, is when she will accept a male," Nielsen says. "This lasts an additional seven to 10 days." During this stage, the vulva will become soft and enlarged.
If your dog is in heat and you do not want her to get pregnant, you should be very careful to keep her away from intact males during this time. "Heat, for both males and females, is very intense and instinctive," Nielsen says. "They will breed through fences and kennels, and have been known to break out windows and chew or dig through doors to get together. It is a strong impulse."
Stage 3: The End of a Dog's Heat Cycle
The last stage of the heat cycle, called diestrus, lasts about two months. It includes reswelling of the vulva and pink discharge, and she will not accept a male. As this final stage ends, the vulva returns to normal and the discharge tapers off. This is the time of pregnancy if your dog mated with a male, though diestrus lasts 60 days whether or not she's carrying puppies.
Stage 4: The Downtime
Anestrus is when your dog isn't in heat. This period of time lasts several months (between three and six months on average, though it varies from dog to dog) before she reenters proestrus.
How Often Do Dogs Go Into Heat?
A dog's heat cycle begins roughly every six months for unspayed female dogs until 8 to 10 years of age.
Nielsen says in her experience, "They seem to show a preference for spring and fall—when the days lengthen and then when it starts getting cooler.
"The first heat cycle, Nielsen explains, will be light and owners may be thinking This is easy! No big deal. "But when the second cycle comes, it's 'Holy crap!'" she says.
Spaying Your Dog
Having your female dog spayed means she will not experience the estrus cycle or pregnancy at all. If your pup goes into heat before you have her spayed, consult with your veterinarian about the best timing for the surgery. In general, it is best to spay before the dog's first heat ever happens (as early as 8 weeks of age), but the procedure can be done once the first heat has finished.
Spaying has benefits outside of preventing pregnancy, including decreased risks of mammary cancer and pyometra (uterine infection).
It’s a girl! Congratulations on your new puppy. Now is the time to read up on everything you need to know about her upcoming life stages, including when she becomes a “woman” that has reached sexual maturity.
Let’s talk puberty: Every female mammal gets a period, but dog periods differ from human periods in terms of process and duration, which we will unpack throughout this article.
We are going to detail everything you need to know about the female dog’s reproductive cycle, what you need to do during her first time in the heat, and help you gauge when is an appropriate time to get her fixed.
Let’s dive into the canine version of the birds and the bees.
What It Means When a Dog Is “in Heat”
Being “in heat” applies to female dogs who have reached sexual maturity. Like with all mammals, it is a process that brings about hormonal, behavioral, and physical changes.
According to Banfield Pet Hospital, you can expect this to happen to your dog about twice a year (every six months) beginning between 6 months of age to 1 year of age. A female dog’s heat cycle is also known as “canine estrus.”
When a dog is in estrus or heat, her estrogen levels increase and then sharply decrease, releasing mature eggs from the dog’s ovaries. At this reproductive stage, she is theoretically ready to mate with a male dog.
Most dog parents spay and neuter their dogs in order to prevent cancer, uterine infections, and animal homelessness. Spaying and neutering have many health benefits as spayed and neutered dogs also live longer lives.
How Long Does a Dog Stay in Heat?
Each estrus lasts for about 21 to 28 days (an average of about three weeks), though this varies between dog breeds and sizes. Smaller breeds of unspayed females, for example, tend to have their first heat earlier than large breed dogs like Great Danes. The American Society for the Prevention of Cruelty to Animals (ASPCA) recommends spaying your dog before she enters her first heat cycle as there’s a slightly higher risk of post-operative complications in older dogs.
How Can I Tell If My Dog Is in Heat?
One of the first telltale signs of a dog in heat is personality and behavior changes due to the shift in their hormone levels. There are three stages of a dog in estrus that are detailed below: proestrus, estrus, and diestrus.
Stage 1: Proestrus
A dog that starts its estrus cycle begins in proestrus. This is the first stage of her heat. In terms of behavior changes, she will start to act more alert, nervous, or on edge. She might stiffen her tail closer to her body as an indication that she does not want to be mated with during this initial phase.
While around other dogs during proestrus, she will likely be a little testy and hide from male dogs. She will show signs of annoyance or aggression, so it is best to keep her away from other dogs and to always supervise her to avoid a potential dog fight.
At this stage, your dog’s vulva will be swollen and there might be an initial bloody discharge.
Stage 2: Estrus
Female dogs indicate they are ready to mate during the next stage, called estrus. When your dog is in estrus she might start to flaunt her rear in front of other dogs or fan her tail in order to spread the scent of her pheromones around.
During estrus, your dog’s vaginal discharge will change to a clear or brownish color. She will also urinate more frequently.
Stage 3: Diestrus
The final stage of the dog heat cycle is diestrus. During diestrus, your dog is no longer showing signs of mating interest, fanning her tail around, and is generally no longer seeking sexual activity. Her discharge will cease and her swollen vulva will return to its normal size.
In Between Heat Cycles: Anestrus
The time between diestrus and the next proestrus is called anestrus. During this time the body prepares itself for the next cycle over a period of four to six months.
Now that you know the signs and stages of a female dog in heat, you need to know what actions you need to take as a dog parent during this time. Read on for information on how to care for a dog in heat in the next section.
What Do I Need to Do When My Dog Is in Heat?
Avoid introducing your dog to other dogs while she is in heat. Pheromones are very powerful during the estrus stage — pheromones can be smelled by other dogs from miles away. During this time your dog is essentially like a sexual magnet.
A male dog tempted by her pheromones will try to mount your dog while in estrus, so you should keep them away from male dogs during this time. An un-neutered dog can get your dog pregnant while in heat.
Other steps to take in order to avoid unwanted pregnancy include strict leash walks and supervision while in the yard. You don’t want your pup to get caught up with a male dog while off-leash, so it is best to avoid the dog park in particular.
There will be some bloody discharge and your dog will likely groom herself during this time by licking. Many dog parents choose to use doggie underwear or dog diapers in order to avoid stains around the house and make clean-up a little easier.
Final Words on the Female Dog’s Reproductive Cycle
The whole process of managing a dog in heat may seem daunting at first, but it’s a totally normal and natural process of their lives. Consider spaying your dog and remember there are many health benefits and added advantages to having her fixed.
In addition to forgoing the whole maintenance process when your dog is in heat every six months or so, your spayed dog will have a longer lifespan. Take note of your dog’s size and breed and remember that small breeds tend to start their heat earlier than large dogs.
As always, ask your vet what the best course of action is for your pup regarding spaying or your dog’s heat cycle.