Key Takeaways
- When Do Dogs Go Into Heat?
- The Female Dog Heat Cycle
- Stage 1: Beginning of Heat
- Dogs & Puppies
- Dog Health Care
- Dog Neutering & Spaying
Here’s what you should know about the dog heat cycle—and other things to expect if your pup isn't spayed.
Owner/president/receptionist/janitor of Goode Girl Media, Lacey Howard lives on a small Iowa homestead with a flock of chickens and 3.5 dogs (it's a long story...but the dog pictured here is Sadie). Needless to say, Lacey is a pet person from a long line of animal lovers, including her grandmother who cared for a rotating collection of birds—emus to parrots to guineas—and other pets (including but not limited to dogs, cows, and a monkey named Chatter).
JoAnna Pendergrass, DVM, is a veterinarian and freelance medical writer in Atlanta, Ga. She is the founder and owner of JPen Communications, a medical communications company that specializes in educating pet parents about pet health and pet care. Dr. Pendergrass is passionate about closing the gap between what the veterinarian says and what the pet parent understands. Through her writing, she empowers pet parents with the medical information they need to make good health decisions for their pets. She is a member of the American Medical Writers Association and the BlackDVM Network. In her spare time, Dr. Pendergrass enjoys spending time with her husband, reading, and being a bona fide science nerd.
- When Do Dogs Go Into Heat?
- The Female Dog Heat Cycle
- How Often Do Dogs Go Into Heat?
- Spaying Your Dog
If your sweet little girl isn't spayed, don't be caught off-guard when she gets her period for the first time. This is the beginning of her estrus cycle, commonly called "heat." During heat, a female dog is open to mating and can become pregnant. 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? Petcare Hub spoke with a veterinarian to get all the answers.
When Do Dogs Go Into Heat?
Your dog can go into heat starting 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 six 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 four months [old] for small dogs!"
The Female Dog Heat Cycle
Just how long is a dog 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: Beginning of 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 bleeding is done, is when she will accept a male," Nielsen says. "This lasts an additional seven to ten 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 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 also the stage that pregnancy occurs in if your dog mated with a male, though diestrus lasts 60 days whether she's carrying puppies or not.
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 eight to ten 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. If your pup goes into heat before you have her spayed, consult with your veterinarian about the best timing for the spaying surgery. In general, it is best to spay before the dog's first heat ever happens (as early as eight weeks of age), but the procedure can be done once the first heat cycle has finished.
Spaying has benefits other than preventing pregnancy, including decreased risks of mammary cancer and pyometra (uterine infection). Talk with your veterinarian to learn more.
