How Long is a Dog in Heat?

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If your female dog still has her reproductive organs she will go through phases of fertility. This page is about how long is a dog in heat?


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September 10, 2013

The canine estrus cycle is divided into four stages: proestrus, estrus, diestrus, and anestrus. Although the first three stages of the cycle are referred to as active heat, the period during the cycle when a non-spayed female dog is receptive to breeding and capable of getting pregnant (in season) usually only lasts from 18 to 21 days. Males will travel several miles to get to a female in season, so to avoid unintended litters, you must be extra vigilant in keeping her away from intact males during this period.

Proestrus (3 to 17 days): This first stage of the heat cycle lasts an average of nine days. The female will emit an odor (pheromones) that attracts males, but in this first stage of the cycle she will reject their advances by jumping, snapping, and growling at any interested males. Physically, you may notice a slight bloody discharge and a notable swelling of her vulva. A few days before estrus begins the bitch may let a male mount her, but she wont stand for breeding. Proestrus ends as soon as she is receptive to the male.

Estrus (7-9 days): The second phase of the heat cycle is called estrus, or standing heat. This is when the female is willing to accept a male for breeding. During this time the discharge changes to a light pink or straw color and the female will often lift her pelvis and raise her tail to the side to signal her readiness to breed. Because she can get pregnant during this time, keeping her safely away from intact male dogs is critical. Estrus lasts an average from seven to nine days (the range is 2 to 20 days) and ends when the female once again refuses to stand for the male.

Diestrus (60-90 days): This final stage in the active part of the cycle begins when the female refuses to stand for breeding. Most males lose interest now, too. The discharge may become redder for a few days before stopping completely and the vulva slowly returns to its normal size. When the discharge and swelling have ended, the heat cycle is considered complete. Diestrus lasts about 60 days, and then merges with anestrus. If the female was allowed to become pregnant during estrus, diestrus lasts until the she gives birth, approximately 63 days after conception.

Anestrus (130-150 days): The fourth and final phase of the estrous cycle consists of little to no ovarian activity. This is the time between the end of one heat cycle and the beginning of a new heat cycle. The length of anestrus varies, lasting on average 130 to 150 days.

Facts about the canine heat cycle:

Females dogs (bitches) become sexually mature when they have their first heat period. This usually occurs between 6 and 12 months of age, although there can be considerable variation among individual dogs and breeds. Toy breeds become sexually mature several months earlier than giant breeds. Sexual maturity does not correspond to physical maturityachieving an adult height and weightwhich generally happens at about 14 months of age in medium-sized dogs.

Ovarian activity and the ability to conceive begin to decline after 6 years of age and ceases (in most females) at around 10 years of age.

Most female dogs will come into heat twice a year until they are spayed. Some may come into heat every five to nine months. Basenjis are noted for only having only one heat per year. The heat cycle is specific for each individual and not influenced by external factors such as hours of daylight. Many females have their first heat cycle at approximately the same age as their mother did.

Although a female dog may be able to physically conceive as young as 6 months, she should not be bred until she is at least 2 years old. There are two reasons for this: 1) a young dog is not yet emotionally mature enough to deal with a litter, which may cause her to harm or abandon her puppies and 2) the common tests used to screen for health abnormalities prior to breeding (hips, elbows, heart, eyes) will not provide accurate results until she is 2 years old.

Some dogs heat cycles get messy, while others are hardly noticeable. Doggie diapers and are available to protect your house, and you may also want to clean her vulva area once or twice a day with a damp cloth to prevent skin irritation. Be prepare for some behavioral changes, too. Your your dog may appear tired, cranky, agitated, attempt to mount other dogs, or try to escape and breed.

Source: Dog Owner's Home Veterinary Handbook, Fourth Edition; The Merck Veterinary Manual, Seventh Edition; Personal Experience.

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March 1, 2011

How long will a dog be in heat? I'm very new at this.

By Annette from Ontario, Canada


March 1, 20110 found this helpful
Best Answer

Usually about three week or 21 days. It is the second week you really need to watch your dog as she can link up with a partner. The third week she is waning down and can still be linking up, but interest is dissipating. The full 21 days you need to keep your female from being alone outdoors as other male dogs will come around; you'd be surprised at how many dogs will appear at this time and dog fights can happen and maybe harm your female. When the female's tail moves toward the side; she's ready for mating. If your dog is going through her very first heat, do not allow her to get hooked up.


She isn't ready or fully matured for it yet and can cause harm to her or a litter. Wait at least for the second heat usually five months after the first heat. Then if you want her to have a litter it's safe. A good breeder does not allow their female dog to have litters at each heat, but alternates to every other one. This is hard on the dog otherwise and creates a lot of complications unnecessarily for the dog and the pups. There are panties made just for the female in heat that you insert a sanitary pad inside and keeps things clean if she's in the house.

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June 27, 2011

How long will dogs be in heat?

By Aryana from CA


June 28, 20110 found this helpful

I think a week to ten days. She'll come into heat and then she's interested but wont let dogs approach her. Then later she'll go into standing heat and that's when she will let dogs approach.


Call your vet, they should be able to tell you. Small dogs might be in heat a shorter time period, though, I'm not sure.

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June 28, 20111 found this helpful

Our dog Mazzy seems to be in heat for at least two weeks, aftetrwards, in about the 60 some days after (when puppies would've been born) she chooses several of her toys as her babies and cares for them just like they were really puppies! We plan to have her spayed because the whole thing is just too heart wrenching!

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June 29, 20110 found this helpful

The only people qualfied to answer this question is your Veterinarian or registered breeder. Remember bitches can have phantom pregnancy. Talk to these two people for the correct information

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June 30, 20110 found this helpful

Are you a breeder? If not, you can have her spay.

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January 7, 2010

We recently got a new puppy. She about 8 months old now and she got her first period on Dec 5th. It's been a month now and she is still spotting. Her vulva is still enlarged which I'm assuming will shrink once her cycle completes. She has Renal Dysplasia so I don't know if that is contributing to a long cycle. I'm wondering when her spotting is going to stop. Any help would be great.

By Todd from Phoenix, AZ


January 7, 20100 found this helpful

21 days is the normal heat cycle. Once the bleeding ends around seven to ten days; a female can begin to mate and in the third week is the waning down time. If your dog has gone past this time period and is still passing blood, I would suggest a vet visit would be in order.

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January 11, 20100 found this helpful

What a beautiful little girl! Since she has Renal Dysplasia, please take her to the vet and don't depend on well-meaning advice from us amateurs. There may or may not be a problem and the vet is the only one who can say for sure. He'll also be able to tell you more about what to expect with her heat cycle.

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January 12, 20100 found this helpful

All pets should be spayed or neutered. It's healthier for the pet, and less stressful for you having to worry about these things. :-)

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March 2, 2015

How long is a dog in heat?

By Christine


December 6, 20170 found this helpful

The average is 12-21 days (but for some dogs it can only last a few days and for others a full month). It can vary from dog to dog and breed to breed, and can be different for the same dog each time.

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December 6, 20170 found this helpful

Usually 2-3 weeks

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April 2, 2015

My 16 month old Whippet just had her first season. It's been 4 weeks now. Is there something wrong?

By Jacqui


April 8, 20150 found this helpful

It should be no longer than 4 weeks.

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