Do Dogs Still Bleed When in Heat? The Surprising Truth


The estrous cycle is an important biological process for female dogs. This article provides an overview of why dogs bleed during their heat cycle, including details on the stages of the canine estrous cycle, how long bleeding lasts, other signs of proestrus, whether a dog can get pregnant while bleeding, how to care for a dog in heat, health considerations, when to see the vet, and more.

The Canine Estrous Cycle

The canine estrous cycle is composed of four distinct stages: proestrus, estrus, diestrus, and anestrus. According to the Cornell University College of Veterinary Medicine, the average cycle lasts 6-8 months, but can range from 4 months to 24 months.

The proestrus stage marks the start of the reproductive cycle in female dogs. This stage can last anywhere from 4 to 20 days. According to East Central Veterinarians, during proestrus the levels of estrogen rise and cause changes in the dog’s behavior and physiology. The vulva becomes swollen and bleeding occurs for 4-9 days on average. This bleeding is meant to attract male dogs (Cornell).

female dog with swollen vulva bleeding

After proestrus comes estrus, also known as “heat.” This is the period where the female is receptive to breeding and will allow mating by male dogs. On average estrus lasts about 9 days. The estrogen levels are still high during this time. The discharge lightens in color and the vulva remains swollen. Behavior changes are most evident during this stage, as the females actively solicit attention from males.

The next stage is diestrus, which lasts 50-60 days on average. According to DVM360, the pituitary gland releases prolactin during this time, which causes progesterone levels to rise. The vulva gradually returns to normal size and there is no vaginal bleeding. The dog will refuse mating from males during this stage.

The final stage is anestrus, which is a resting period of 120-150 days on average. The reproductive system is inactive during this time and no signs of heat will be exhibited. After this resting period, the cycle starts again with proestrus.

Why Do Dogs Bleed When in Heat?

Dogs bleed during the proestrus phase of their reproductive cycle, which is the period leading up to when they can get pregnant (estrus). During proestrus, a dog’s ovaries start producing more estrogen, which causes changes in the uterus and vagina.

The estrogen causes the cells in the lining of the uterus to proliferate and grow. Small blood vessels also develop in the uterus lining during this time. The thickened uterine lining is meant to support potential pregnancy and embryo development if the dog becomes pregnant during her heat cycle.

However, if the dog does not get pregnant, the uterine lining is not needed, so it will shed. The shedding and breaking down of the uterine lining is why dogs have a bloody vaginal discharge during proestrus. The bloody discharge contains both blood and cells from the lining of the uterus.

According to, the bloody discharge lasts for around 7-10 days on average, but can be shorter or longer depending on the dog.

How Long Does Bleeding Last?

The duration of estrus bleeding in dogs typically lasts about 7-10 days on average. However, there can be some variation between breeds and individual dogs. According to the Kennel Club, most dogs bleed for roughly 7-10 days, which is around half of their total 21 day estrus cycle.

In general, larger breed dogs tend to have a heavier and longer estrus bleeding phase compared to smaller breeds. For example, a Great Dane may bleed for 10-14 days while a Chihuahua may only bleed for 4-7 days. Other factors like age, health status, and if the dog has had a litter before can also impact duration.

It’s important to track your dog’s cycle and note how many days the bleeding phase lasts. That will help you predict when to expect her next heat. If the bleeding persists longer than 10-14 days or seems excessively heavy, it’s a good idea to have your vet examine her to rule out any underlying issues.

During proestrus when bleeding occurs, the female will not accept a male yet for breeding. Bleeding signifies rising estrogen preparing for estrus and ovulation. Once bleeding ends and estrus begins, your dog will be receptive to males for breeding.

female dog no longer bleeding as enters estrus phase

Other Signs of Proestrus

In addition to vaginal bleeding, there are other changes in behavior and appearance during the proestrus stage. As estrogen levels rise, female dogs will start to attract male dogs, but they will not allow mating at this point. Behaviors during this time may include:1

  • Increased urination
  • Swollen vulva
  • Male dogs showing interest
  • Excessive licking of the genital area
  • Restlessness and nervous behavior
  • Appetite changes

The vulva will become swollen and enlarged, and a bloody discharge will be visible. This discharge starts off red, but becomes lighter in color and watery over the course of the phase. Proestrus typically lasts around 9 days.2

Can a Dog Get Pregnant While Bleeding?

Yes, a dog can get pregnant during the bleeding phase of her heat cycle, which is known as proestrus. During proestrus, bloody discharge from the vulva occurs as estrogen levels rise and eggs in the ovaries begin maturing in preparation for ovulation. Though bleeding signals the start of the heat cycle, ovulation occurs later on during estrus when progesterone levels increase. This means that while a dog is unlikely to get pregnant at the very start of proestrus, she can get pregnant for a good portion of the bleeding phase as ovulation approaches. According to veterinarians, the fertility window begins roughly 5-7 days into proestrus once the bleeding lightens and becomes watery. This fertile period overlaps with the end of bloody discharge as the dog transitions from proestrus to estrus. The chance of pregnancy increases as bleeding tapers off and the female begins flagging and allowing mating.

In summary, the bloody discharge associated with proestrus does not prevent pregnancy. A dog’s fertility peaks in the final days of bleeding and continues through estrus until progesterone drops off. Owners should take steps to prevent unwanted breeding for the entirety of the heat cycle, including the bleeding phase. Isolating the dog or using pet diapers can help avoid accidental matings. Discuss contraceptive options like hormone shots with your vet if you wish to prevent pregnancy during future cycles. While bleeding indicates pending fertility, it does not mean a dog cannot get pregnant during this time.

Caring for a Dog in Heat

When a female dog enters her heat cycle, owners need to take special care to keep her comfortable, clean, and safe. Here are some tips for caring for a dog in heat:

Exercise caution taking her outside for walks. Keep her leashed and avoid off-leash areas like dog parks where intact males may be present. It’s best to only take her out to relieve herself during this time.

owner walking female dog on leash while in heat

Consider doggie diapers or sanitary pads to help contain any discharge and prevent stains. Change frequently to keep her clean and comfortable.

Increase attentiveness and limit unsupervised time outside. Even in a fenced yard, a male can detect a female in heat from far away.

Provide interactive toys to help keep her mentally stimulated when she can’t exercise as normal. Food puzzles, Kongs, and chews are good options.

Speak to your vet about the best food and supplements to support her needs during this energy-intensive time. Things like zinc and vitamin C may help.

Prepare a comfortable and quiet space for her to rest indoors during this time, such as a crate with bedding or a separate room.

Gently discourage clingy behavior and don’t reward it with excessive affection. Set up a routine with regular engaging activities.

Thoroughly clean any discharge on floors or furniture right away. Use an enzymatic cleaner made for pet stains.

Talk to your vet about spaying. Spaying before the first heat offers health benefits. If waiting, carefully plan the timing.

Keep a close eye on her behavior during her cycle. Drastic changes may indicate a health issue needing veterinary attention.

Health Considerations

There are some health risks and issues to monitor when a dog is in heat. According to PetMD, dogs can experience side effects from the hormonal changes associated with estrus. These include:

  • Weight gain – The increase in hormones can cause dogs to eat more.
  • False pregnancy – Some dogs can show mothering behaviors like nesting after estrus.
  • Hemorrhage – Very heavy uterine bleeding is possible.
  • Mastitis – Mammary gland infection may occur during or after estrus.
  • Pyometra – Bacterial infection of the uterus is a serious risk.

female dog showing signs of false pregnancy

Owners should watch for signs of these conditions and contact a veterinarian if concerned. Special care may be needed for dogs prone to heavy bleeding during heat. Monitoring weight is also recommended to avoid obesity. Ensuring the dog gets adequate exercise can help. Overall, owners should be vigilant about their dog’s health and comfort when she is in heat.

When to See the Vet

There are certain signs during a dog’s heat cycle that warrant a visit to the vet. These include:

  • Bleeding that lasts longer than 21 days. Prolonged bleeding could indicate an issue like uterine infection or uterine tumor. Most dogs bleed for 7-10 days.
  • Signs of illness like lethargy, vomiting, or diarrhea during the heat. These could be signs of infection that require medication.
  • Abnormal discharge, like pus, which could signal pyometra, a life-threatening uterine infection.
  • Not going into heat by age 2. Delayed puberty may suggest an underlying health issue.
  • No heat cycles for over 6 months. This may indicate ovarian issues or hormone imbalances.
  • Weak, excessive bleeding or pale gums, signaling anemia.
  • Swollen vulva that persists beyond the heat, which may mean an infection or tumor.

It’s a good idea to make a vet appointment if you notice any of these issues arise during your dog’s heat cycle. The vet can run tests to diagnose the cause and provide any necessary treatment.


To summarize, dogs bleed during the proestrus stage of their estrous cycle as their reproductive tract prepares for potential pregnancy. During this stage, increasing estrogen levels signal the uterine lining to thicken and start shedding. This explains the visible vaginal bleeding. The bleeding usually lasts for about 7 to 10 days but can range from 2 to 21 days. Other signs of proestrus include swollen vulva, appetite changes, and behavioral changes. During this stage, a dog can become pregnant if bred. To care for a dog in heat, provide proper nutrition, gentle walks, and keep her away from intact males to prevent unwanted litters. Monitor for abnormal discharge or prolonged proestrus bleeding, and consult your vet with any concerns. In conclusion, vaginal bleeding is a normal part of the canine heat cycle and indicates ovulation is approaching.

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