The Female Dog Heat Cycle: Is it a Period?

Last updated:November 27, 2024

WOAH—you’ve adopted a female dog and suddenly she’s bleeding from her private parts! What on earth is happening? Before you panic, I’m here to tell you that intact (not spayed) female dogs do have periods, sort of. While not the same as a human menstrual cycle, this bloody discharge is part of what’s called the estrus cycle in dogs.

This is a normal part of her reproductive system and it’s nothing to worry about in most cases. Let’s explore what’s happening when your dog has her period and what signs to look for in your lady pup that suggest she may need to see a vet.

What is the Estrus Cycle in Dogs? 

Understanding the estrus (or heat) cycle can help you provide better care for your dog and give you peace of mind. Similar to human women, female dogs have a reproductive cycle that prepares their bodies for pregnancy.

The estrus cycle, commonly referred to as being “in heat” or “in season,” involves hormonal changes that signal the body to prepare for mating. You may notice several changes in your dog’s behavior, as well, which we’ll discuss later.

It’s important to understand that just because a female dog has her first heat cycle, it doesn’t necessarily mean she is ready to mate and have puppies. Pregnancy can be very difficult on younger dogs (and elderly dogs) and even cost them their lives. Many other factors can influence when your dog goes into heat, as well.

Factors that Affect the Timing of Heat Cycles in Dogs Age 

Most female dogs experience their first heat cycle around 6 months old, but it can vary depending on breed and size. Giant breeds, like Great Pyrenees and St. Bernards may not go into heat until around 1.5 to 2 years old.

• Nutrition and Health: Severely underweight or sick dogs may not have regular heat cycles because their bodies are focused on getting better instead of preparing for pregnancy.
• Chronic Illnesses: Conditions such as Cushing’s or Addison’s Disease that disrupt the normal hormone balance could also interfere with the timing.
• Climate: Long summer days with more sunlight may trigger an earlier cycle, while short winter days may extend the time between cycles.

The Four Stages of the Canine Heat Cycle 

The estrus cycle in female dogs consists of four stages. People notice the first stage most often because it’s when they see bloody discharge like a period. Here’s a brief overview of each stage.

Stage 1: Proestrus

During this first stage, you’ll notice some physical changes in your female dog. The vulva becomes swollen and may produce a thin, bloody discharge. Your girl might become more restless—increases in pacing, panting, or vocalizations are common. 

She might also urinate more than normal. You might also notice she asks to go outside more or may try to escape from the yard. Proestrus usually lasts about 7–10 days but can last up to 27 days. Male dogs will become very interested in her but most females won’t allow them to breed at this stage.

Stage 2: Estrus

The second stage, estrus, lasts about 5–10 days (though some females remain in estrus for up to 24 days). This is when female dogs are fertile (able to become pregnant) and become more receptive to male dogs. You might notice male dogs hanging around your yard or trying to get to her.

The bloody discharge should slow down or stop as this stage progresses. If she mates, ovulation happens about two to three days later. Ovulation is when eggs move from the ovaries (where the eggs are made and stored) to the uterus (the womb, or where puppies grow).

Stage 3: Diestrus

This is the post-heat stage where the body returns to normal. Diestrus can last anywhere from 10 to 140 days. If your dog has become pregnant, you won’t see many differences at this stage. Be sure to check out our article about dog pregnancy, week by week!

Stage 4: Anestrus

This is the resting phase between cycles and lasts about six months. Most female dogs have 2 heat cycles each year. However, small breeds, like Chihuahuas and Dachshunds, may go into heat as often as three to four times a year. In contrast, large breeds, such as Newfoundlands and Alaskan Malamutes, might only experience heat every 12 to 18 months. 

Since the timing can vary significantly, it’s important to monitor your dog’s specific patterns. 

Behavior Changes When Your Female Dog is in Heat 

When a female dog goes into heat, you might notice several behavior changes. Some dogs become more affectionate, while others want to be left alone. You may see signs of restlessness, like pacing, panting, or escape attempts. She might also mark her territory, both indoors and out. These changes are natural as her hormones fluctuate.

Remember, every dog is different; some female dogs may show some, all, or none of these changes along with others. You know your dog best, so watch for signs outside her normal behavior.

When Should a Dog’s Period Prompt a Trip to the Vet? 

The estrus cycle is normal for female dogs that haven’t been spayed. However, there are a few signs that indicate your dog needs to see a vet. If your dog is currently in heat or was recently, watch her closely for these symptoms.

See also

Pyometra

If you notice a foul-smelling or pus-like discharge from her vulva, contact your vet as soon as possible. While severe urinary tract infections (UTI) can cause similar symptoms, the more likely cause is pyometra. Pyometra means “pus-filled uterus” and it’s a serious emergency. 

This condition can become life-threatening if the uterus ruptures, allowing the infection to escape into the body cavity leading to sepsis (widespread infection).

Tip: Most vets don’t recommend using doggie diapers to keep the mess to a minimum because they can hold moisture against the vulva and lead to pyometra and UTIs.

Other Concerns

Keep an eye out for these additional symptoms that could indicate a more serious problem:

• Lethargy
• Vomiting/Diarrhea
• Loss of Appetite
• Excessive Thirst and/or Urination
• Swelling in the Abdomen

Contact your vet immediately if you notice any of the signs or become concerned about your dog for any reason during or after her heat cycle. It’s better to be safe than sorry!

Do Female Dogs Have Periods? (Sort of)

Being aware of your female dog’s heat cycle helps you take good care of her during this time. While the estrus cycle is a natural process, monitoring for concerning signs could save her life. If you notice anything out of the ordinary or have doubts, don’t hesitate to consult your vet. 

Vigilance and proactive care ensure your lady pup remains happy and healthy through her heat cycle. If you want to avoid the whole shebang, consider getting her spayed as soon as possible!