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Signs & Stages Of The Dog Heat Cycle

↯ Key takeaway points

  • Female dogs reach sexual maturity between 8 and 18 months of age.
  • Healthy bitches come into heat every six months on average, but this can vary between breeds.
  • The heat cycle of a female dog has four stages: proestrus, estrus, diestrus, and anestrus.
  • Signs that a female dog is in heat include bloody discharges, a swollen vulva, tail flagging, male interest, and mood changes.
  • The anestrus stage is the quiescence stage and lasts until the next cycle starts, generally after four to five months.
Breeding Business is passionate about all sorts of domesticated pets. They have written dozens of articles across the web.
Zoo and wildlife doctor in veterinary medicine passionate about animal welfare and preventive medicine.
Published on
Friday 18 September 2015
Last updated on
Monday 6 November 2023
The Stages of The Dog Heat Season Cycle
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Females reach sexual maturity (puberty) between 8 and 18 months of age, there is tremendous variability in the maturation age between breeds, and even within a breed. From then on, a healthy bitch will come into season every six months on average, some breeds can come into season only once a year or quarterly. The latter bitches are usually not fertile in every season.

When a female comes into heat or season, her body is preparing for mating and the possibility of producing a litter. A successful mating only happens when you have an understanding of your female’s heat cycle and know when is the best time to let the actual copulation happen.

This article has two main sections. The first one goes through the different stages of each bitch heat cycle, while the second section goes through the symptoms and signs to expect when your bitch starts one of her cycles.

UPDATE: If you simply want clear answers to your dog heat cycle questions, check out our dog heat cycle FAQ.

UPDATE: we’ve written a comprehensive article about the abnormalities in the dog heat cycle.

Bitch Heat Cycle Diagram
Diagram showing two heat cycles, back to back.

The Bitch’s Heat Cycle

A normal heat cycle lasts approximately three weeks, within which the bitch will go through different stages.

The Proestrus Stage — Getting Ready

Lasting around 9 days, this first stage is marked by the eggs in the ovaries beginning to mature and the estrogen levels start rising.

Proestrous Vulva
Comparative image of the vulva of an anestrous bitch (left) and a proestrus bitch (right) – (Credits to The Visual Guide to Canine Reproduction)

Physically, the female’s vulva lips typically swell up and become pliable, you may also notice some bloody discharges. Her body is pretty much getting ready, day after day, to receive the male’s penis but during the Proestrus stage, the female will not allow mating. At that time, males are attracted to the non-receptive female and she may react aggressively to get rid of them.

For hygienic reasons, and for practical reasons, if you are planning a mating, you may want to trim your bitch’s hair around her vulva and genitals. It will be much easier for her to groom herself, and for the male to mount her if you are organizing coitus during the next stage, the oestrus stage.

If you have male dogs in your close neighborhood or even at home, and you do not want your bitch to mate with them, it is highly recommended to keep the males away from her to avoid the annoyance and little fights between the dogs.

Dog Mating First Stage Coitus
The first stage of the coitus between a male and a female dog. (credits: unknown)

The Oestrus Stage — Mating

Oestrus is the next stage, also lasting around 9 days, where eggs are released from ovaries and the estrogen levels decline while progesterone levels rise.

Here, male and female are both attracted to each other and the bitch will typically ‘flag’ her tail as if showing the male that she is now allowing access to her vulva. It is only during this Oestrous window that pregnancy will result from copulation or artificial insemination. As per Dr. B. Eilts from Louisiana State University School of Veterinary Medicine: during estrous, females may have clearer bloody discharges than at the proestrus stage.

Proestrus and estrous stages can last anywhere from 5 to 21 days each, the length varies greatly between individuals. Both these stages together form what we commonly refer to as the “heat.”

The Diestrus Stage — Pregnancy (or not)

This third stage is the period following mating, it commonly lasts 58 to 63 days in a pregnant female and 60 to 90 days in a non-pregnant female. Progesterone is dominating and the female will refuse a male’s advances during this stage.

Dog pregnancy stages timeline chart
Timeline of the dog pregnancy stages. (credits: unknown)

This stage may be delicate for bitches that are not used for breeding as the long exposure to the progesterone hormone may lead to a condition called pyometra, if the bitch is not spayed. Also spelled Pyometrea, this condition can happen at any age, whether the dog has bred or not, and occurs when the uterus fills up with pus, bacteria, and white blood cells. Pyometra is can lead to death if left untreated, usually because of toxins infecting the dog’s bloodstream or the uterus rupturing. Thus, it’s eminently recommended to spay a bitch that is not going to be mated.

The Anestrus Stage — Quiescence & Recovery

Sleeping Dog

The last stage is the quiescence stage for the bitch and it will last until the next cycle starts, generally after four to five months.

After pregnancy, fertility is very low if the bitch has not attained 90 days of anestrus, indeed, a female needs enough time to repair her own uterus or she will not be able to cope with a new pregnancy. Her sex hormones are at their lowest throughout the entire oestrus cycle.

Signs That Your Female Comes Into Season

There are several signs to look out for when your bitch is starting her cycle and the list herein will give you further details. There could be only one sign showing at first so you need to read your bitch attentively to realize it within the very first days.

Don’t forget to take a look at our very informative dog whelping timeline.

Bloody Discharges

First on this list because usually the surest sign of being in season, your bitch will start to have pinkish discharges during the first stage, to then become brighter or tanned.

Some females clean themselves very well so it may be hard to notice. Please note, it is important to not mix bloody discharges due to the start of the heat cycle with anal gland secretions that have a rather overwhelming smell.

how to calm bitch during her heat season

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Swollen Vulva

Easily noticeable, your bitch’s vulva will swell within a few days. You may be unlucky if you are having a female who hardly swells at all but the vulva usually swells up with a spongy look.

Tail Flagging


As soon as the estrous stage starts, your bitch will be ready for mating and breeding. To send signals to nearby males, the bitch commonly holds her tail up and moves it from side to side to disperse her scent and attract the males near her.

Male Interest

Three miles away is the distance from where a male dog can detect that your bitch is in heat. As soon as her cycle starts, you will notice a lot of males dogs getting closer to your bitch and even hanging around your yard. An over interest expressed by several (random) male dogs is a clear sign of a heat cycle starting.

Mood Change

Similar to the women’s premenstrual syndrome, some bitches can turn to an over-sensitive mood and become a bit contentious with people and other animals around them.

Swollen Nipples

Not very common, some females may have their nipples swollen a little bit. It may be hard to notice for us, though.

86 comments on “Signs & Stages Of The Dog Heat Cycle”

  1. Melba Dowding

    Our old, neutered bitch who is now 13 has suddenly become attractive to male dogs.

    . They always want to sniff and lick her rear end. Is this normal? do older bitches smell differently? n She is fine in herself and enjoys two walks a day.

    1. Hi Melba, there are several potential reasons to this.

      1) Males may sniff her rear end because they smell other odours: is she incontinent?

      2) Perhaps she has an empty stomach and some gas?

      3) Very rarely, when neutering a female, the vet forgets small tissues behind and after some years, these grow and it triggers some brain mechanisms that show some heat signs even if she can’t be impregnated at all. But it is very very rare and only read online; never encountered this.

      4) Most likely she ate something lately and just like with us, what we eat influences the smell, texture and color of what comes out. Males perhaps are sensitive to that.

      1. Unfortunately we have encountered the “left behind tissue” Our previous vet said she must have accidentally left part of an ovary causing the heat signs and scents in our spayed Bernese Mountain Dog. She offered to go back in and “try to find” this left behind tissue, at no cost haha But we knew that would be like finding a needle in a haystack at this point. We were not comfortable with our pretty girl going under for a stupid mistake like that. After too many mistakes from this clinic we finally realized that they obviously did not have our animals health care at their best interest and the almighty dollar was the only reason they went to work each day, so we ultimately fired them and moved on to a fabulous, caring vet.

        1. Unfortunately the case for too many veterinary clinics…

  2. Michele

    If our male shepherd is licking our females butt and hangs around her butt constantly does that mean she is going into heat?

  3. Very likely she is near or in her heat if she attracts male attention. If she is not happy with it then she is near her heat, and if she is welcoming then she probably is in heat.

    1. Briteney P. Fortson

      My dog is 12 months I believe and yesterday I saw redish pink like blood on her vulva I cleaned her off but as I did she began to tuck her tail also she’s been a lot Moody.
      A week before this I took her to my friends that has a male dog and she was a snappy a little. But would let him lick her and some what smell her. He tried to mount be she wouldn’t allow him and he began to whine. Doea this mean shes in heat?

      1. Usually, during the first 7-10 days of the heat, the female attracts males but she doesn’t want them anywhere near. The second part (10 days also) is where the female still attracts males and this time is receptive to their attempts.

        So she probably is in heat or definitely getting there.

  4. Tracey Newcombe

    I have a female staffy cross just turned 12 mths, shes had a season in March next one in September, her nipples have really dropped, look full, no milk though, I know shes not pregnant, she was 9mths old when I “saved” her.
    I was out walking her earlier and notice she has a discharge from her lady bits which looked like longline spit, I have no idea what this is can you help please. I was told it could be a phantom pregnancy, is there any advice please ? Im hoping to have her spayyed in August. Thank you

  5. Praysis

    It was very unfortunate that my dog’s spay was botched, the veterinarian left one ovary inside and later I noticed blood and I immediately called him and he said he didn’t remove both ovaries because that would lead to overweight and I knew he is wrong; it all depends upon diet and exercise. I want to know that should I get her operated again for the removal of second ovary? Does this have harmful affects?

    1. As a standard rule, if we can avoid performing an surgical operation then it’s obviously better.

      Leaving one ovary could lead to some medical risks in the long run so I would call up three or more vets around you (or not) and ask for advice.

      Your own vet doesn’t seem to be on top of things.

      You can also visit

  6. Liberty

    Can a nine month old male dog successfully cross a 17month old female dog?.

    1. If both the male and the female are sexually mature, and the female in heat. Then yes.

    2. Regina I Floyd

      Mine did

      1. Harkomsvilla

        That’s what happened to mine dog,he was fucked by neighborhood dogs who was nine months male dog

  7. I have a 4 yrs old pit mixed with lab and she showed the first sign of bring in heat she had the blood n the swelling and now it looks like it has now swelling but still very little discharge what does that mean

    1. She is definitely showing signs of being in heat. Not all bitches in heat show all the signs with the same intensity so take notes and you will be more aware next time it happens!

  8. Angel Galvan

    My German Shepard has a reddish liquid on her fur near her vulva at all her fur near there seems to be wet but it doesnt have a color and so i was wondering is she is ready to mate she did put up her tail up near a barking dog but i dont know if it was a female or male but all the time walking before that her tail was down.

    1. Timing is difficult the figure out with symptoms only. The best person to answer that would be a vet using hormone testing. She will be ready to mate when she will be allowing male dogs near her, licking her and mounting her.

  9. Sharon

    What determines the amount of eggs dropped by the female during heat cycle? My 3year old yorkie has had only one puppy in her last two cycles in the last two years! She is 6 lbs. and in good health! Is there an estrogen supplement that would help produce more eggs?

    1. The egg count depends on so many variables that are impossible to control:
      – how many eggs are released by the bitch
      – how many of these eggs are fertile
      – when is the mating taking place (not too early, not too late)
      – how good is the stud’s sperm

      So many factors :)

  10. Damflix

    Is it too early to breed ur dam on d 8th day? How can u boost ur stud’s sperm? (will milk help)

    1. Nothing will help bar a healthy lifestyle (diet, rest, and good genes!) — we can’t predict the day as it will depend on your bitch’s heat and fertility on that given cycle. Your vet may hormone test her and indeed give you the best date to organise the mating.

  11. Megan

    My female is getting aggressive towards my neutered male. Could this be a sign of season as it has never happened but shes gone for hims 6 times in the past hour? X

    1. Definitely — might not be but usually females tend to be aggressive towards males during the first week or two of their heat.

      Then, they let them approach and are super friendly (second phase of heat.)

  12. DAVID

    I have a 20 months old female South African Boer Boel. I noticed her vulva was swollen and bloody discharges and stains in her cage last week. A neighbours male boer boel was kind enough to mount her after several failed attempts. however, its now two days since the mating but i still notice the bloody stains in her cage. Please is this normal? 2. Could this mean she has not taken in (pregnant) yet.

  13. Lynne

    My Labrador had a season 12 weeks ago and is now showing a pink discharge again. She usually has a season about 6 months apart. Is it something I should worry about ? Does she need to see our Vet ? She is about 10/11 not sure because we got her has a rescued dog 5 years ago

  14. Sylvia Regan

    I have a jack russel female dog I know she is on heat but not sure what stage, she has become more moody and is not interested in her food any more, I know she is mot pregnant as she only goes out with us or is in the garden and there are no more dogs around us. We rescued her in november 2015 and this we think is her second season ( with us) as we dont know her history she wasn’t like this the first time, can you please give me some sort of clue to what might be going on with her.

    1. She is probably within the first week or two of her heat. That’s when they usually have mood swings and are not behaving like they usually do. Give her more time :)

  15. Sarah

    We are wanting to breed our bitch and took her to an accredited breeder day 11 and my girl did not allow him to mount her how long shall we leave it to introduce again? The vets said I’ve missed the boat to get an ovulation test so have to wait for the tail flag but my beagle always has her tail in the air or wagging! Today is day 13 with the odd drip of light brown fluid.

    1. It is probably because the bitch isn’t ready yet (too early) or you guys passed that window (too late.)

  16. Jackie

    Thank you for this great post! My bitch is in heat and I was a little concerned about her mood swings but everything’s clearer now.

  17. Gift joy

    My dog is on heat..and she cries in the night..why is that?

  18. Val

    My 15 month old toy poodle has been bleeding for 11 days. Yesterday and today her cleaning herself is really frantic. I’m concerned she’ll make herself sore with it. Is this normal?

    1. This is very normal. Bitches (in heat) clean themselves as much as possible. They don’t always get it right and that’s why we get some blood on the carpet or the bed. Definitely let her keep on cleaning herself up.

      1. Val

        Thank you. I’ll relax now.

  19. AMOS

    please, how many months will it take a caucasian to come of first heat?

    1. Caucasian Shepherd Dogs are a giant breed so they can have their first heat a year in or so. The duration of the heat is similar to other dogs, 1 week to be on heat, 1 week on heat, 1 week to come off heat.

  20. AMOZ

    thanks alot for your respond, please i am new in dog breeding, how will i count the days and also to know the best day to breed my dog? thanks.

  21. Cris

    If a bitchh is mated will that end the heat and begin pregnancy or will heat continue to normal end?

    1. Lazhar

      It will continue until the end. Therefore, it is possible for a bitch to give birth to a litter with puppies from different fathers.

      1. Cris

        If a bitchh is mated will that end the heat and begin pregnancy or will heat continue to normal end?

        Thanks so much for your reply :)

        1. The heat will continue until its normal end even if the bitch is pregnant. This is why a bitch can give birth to puppies from different fathers.

  22. ADESOCA.

    I have a boar boel dat is 50 days gone in preg….but i noticed ds particular signs;
    1. poor eating habit or not at all…just taking water.
    2. very BIG swollen vulva almost ×20 normal size.
    3. and drying up of d nipples.

    What advice can u provide and how many days is she due…THANKS.

    1. You should start using nutrical or high-calorie health supplements to make sure she gets enough calories to have a healthy litter and a nice labour. She needs energy but definitely is losing appetite, which is normal when getting close to whelping day.

      Check this post out abotu weight gains:

  23. AMOZ

    HELLO, my Caucasian is 12 months now, but she have not yet started her first heat, Pls what is the solution? thanks hope to hear from you soon.

  24. Will

    My Caucasian Shepherd just started her first heat at 7.5 months of age. Although larger breeds go into heat on average later, it is all up to individual dogs.

  25. AMOZ

    Yes, i know larger breed starts their heat late, i have the same Caucasian breed with a friend of mine, the first dog start heat at 7 months while the other starts at 9 months.

    mine is 12 months now and nothing is happening.

  26. pls I ave a Caucasian female of 2years DAT only sees pulse on her vulver but doesn’t come on heat, wat can I give 2 her 2 come on heat

  27. ashlei

    When a dog enters heat, do they bleed first, then breed. Or do they breed then bleed? I’m so confused. My dog is in her first and we have a male, but are trying to let her mature further before a litter.

    1. Hi Ashlei – a heat lasts approximately three weeks (one week coming in, one week of mating window, one week coming off). A bitch usually starts bleeding from the first days while breeding can only occur in that second/third week because before then, a bitch won’t allow mounting.

      1. Deanna Fuller

        My pug started to come into heat on the 16th and today’s the 26th when will she be ready to mate I had the mail pug here for the last 3 days and they haven’t done the wild thing but they’ve been trying please help me

        1. Let them be together – they will do it when she is ready to do it, probably within hours or days.

  28. AMOZ

    i breed my dog and she is having lost of appetite please what is the cause for it

  29. Tracey

    I have a male and female 7 month old yorkie puppies and a neutered 3 yo pit mix. My bitch is definitely show signs of being in heat the last 3 days. When do I have to began to keep the males away from her and do I have to keep the neutered male away from her as well. I’ m pretty freaked about all this. She was going to be spayed next week to avoid this. So, now how lobg do I have to wait to get her spayed ?? Ugh

    1. Wait after her heat ends and ask your vet for the best moment do to it depending on her hormonal levels. In the meantime, keep all males away from her.

  30. Vince

    My pug has been on heat when she was 6 months, now she is 2 years old, and she had not her second heat. I am worry about that.
    Do anyone know if that is normal or she needs be seen by a vet?

  31. J

    I did AI with my female i think I might have done it a couple days after she was done flagging. Does that mean I completely missed the opportunity to get her pregnant or is there still hope?

    1. Hello J – flagging isn’t a surefire sign of the female dog’s heat or estrus stage. Hormone testing is a lot more accurate. It’s impossible for anybody to say for sure if you missed it or not just by the timing in reference to her flagging tail.

  32. Simon llewellyn

    I have a Labrador bitch 3 1/2 years old but I have never seen her in season . Is this normal. I have a 3 year old ess and she comes into season regularly. Is there anything I should be doing or looking for

  33. Carol Adams

    I have a 2yo golden retriever with a great pedigree, dna, ofa. She refuses to mate. I have heard that some females will never accept a male or that it could be years before she gains enough maturity. Is this true?

    1. Definitely true, sometimes it also depends on the male’s behaviors.. Some males are too shy… Or at times, it’s the wrong timing (sometimes a day before or after is just not the right day anymore.)

  34. Carol Adams

    Also, she is having normal heat cycles every six months.

  35. Lisa

    Hi I have a 8 month cane corso bitch and have been keeping an eye on her and although no swelling or blood of Vulva there is almost a baggyness with swelling under her tail that I’ve noticed could this be related ?

    1. Definitely! A swollen vulva is extremely common during heat!

  36. Sandra L Ellis

    My 5 month old pit has white discharge..also male dog hanging around. Isn’t she to young?

  37. Tonya

    What’s the earliest a female can be ready to breed? My female started flagging and standing for my male on day 4.. She’s on day 13 and the attention has died down… Could she have already passed her prime stage? They’ve been together since day 1 just in case..

  38. Jody

    My female golden retriever just started her second heat cycle. Her first cycle was almost 14 months ago. Does this mean her cycles will be 14 months apart on average, or can they vary?

  39. Frances

    Hi I have 2 6month old puppies both from the same litter, they normally get on famously, that is until Wednesday when one of them went into be spayed, the second puppy came on heat the week before & everything was fine between them until we picked up the first puppy from the vets following her surgery,ever since then we can’t leave them alone together as the one on heat has turned extremely aggressive towards her sibling & I mean extremely aggressive, in fact I think if we were not in the room with them she would do her sister some serious damage.
    Please help.

  40. mark puddy

    how can i tell if my 9 month old lab has gone thru a heat cycle yet?

  41. Diana Yost

    I 8 month Golden/Irish setter is in heat she eats very little not like she use too. What can I do so she will eat. She gets homemade food.

  42. Brenda

    my females goes into heat anywhere from 5 .5 to 6 months a year is this normal?

    1. Brenda

      what I meant is that she goes in heat twice a year but not every 6 months but sometimes it is 5.5 than others it is 5 months twice a year so it is so hard to get the correct time to breed her??

  43. Sharon

    I have a year old German Shepard. She is approaching the end of her heat cycle. The material she is passing stinks! It appears to be good blood, it just has an odor. Is that normal?

  44. Myra Pitman

    My 10 month old Yorkie just came off of her 1st real heat. Now the area around her nipples , about the size of a quarter is hard. What could that be? I’m almost positive she did not get bred. She wore panties and stayed away from the male. Is this normal and when will it go away, or be back to Normal ?? Scared for my little one. I don’t want to breed her until she is 2.

  45. Cheryl Henlsey

    how can I help get a young (18 months) virgin stud interested in my bitch?

  46. Donna

    Hi my Siberian husky came in to heat 9 days ago today her bleeding as changed colour and she is acting like she wants to dominate or maybe feeling frisky towards me had a blood test for her on day 8 which was 1.16 she is flagging and acting more out of character for her she is just over 2. Could she be ready to mate even if her progesterone levels are low?

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