The four stages of a dog's heat cycle: proestrus, estrus, diestrus, anestrus
A dog's cycle has four stages. Two of them you can see, two you cannot. Knowing all four explains why she snaps at every male on day 3 and goes looking for one herself on day 12, and why milk suddenly appears six weeks after the heat.
1. Proestrus: about 9 days
What happens: The ovaries grow follicles and oestrogen rises. The uterine lining becomes more supplied with blood, hence the bleeding. She is not fertile yet, but her scent already attracts males from far away.
How you recognise it: The vulva swells, bloody to reddish discharge, frequent marking on walks, often days before the bleeding, more licking. Males become attentive, she rejects them, sits down or turns away. Many dogs are restless or clingy.
What you can do: Note the first day. From now on always on the leash, even where none is required; choose quiet times and routes; avoid the dog park, training class and club ground. Protective pants only indoors and only for hygiene. Note bleeding, vulva and behaviour daily.
See the vet if the bleeding is very heavy, she has a fever, is apathetic or the discharge smells foul.
2. Estrus (standing heat): about 9 days
What happens: Around the start of standing heat comes the LH surge, about two days after it ovulation. The eggs then mature for another two to three days and are fertile for two to three days. Sperm survive up to a week: a mating at any point in this stage is enough for a pregnancy.
How you recognise it: Discharge turns lighter, pinkish to straw-coloured, and less; the vulva softens. She stands for the male, flags her tail to the side, presents herself and goes still when touched above the tail. She actively seeks contact and may run off.
What you can do: Never unsupervised now, not even in a fenced garden; secure doors and gates. Separate males in the household; even neutered males can still be fertile for up to about six weeks after neutering. If breeding is planned: progesterone at the vet from about day 5 to 7 of the heat, counted from the first day of bleeding, every two days. More under When is a dog fertile?
See the vet immediately after an unwanted mating. There are ways to prevent a pregnancy; your vet decides on the best timing, often only after standing heat has ended. Also if standing heat lasts longer than three weeks.
3. Diestrus (metestrus): about 9 weeks
What happens: The corpora lutea produce progesterone whether she was mated or not. Hormonally the body prepares for a pregnancy. When progesterone drops at the end, prolactin rises: this is how a false pregnancy can develop.
How you recognise it: The vulva shrinks, discharge becomes yellowish-mucous and stops. In the first one or two days she may still accept a male. After that no outward signs; some dogs are calmer or eat more.
What you can do: Stay careful for the first two days, then normal walks and the club ground are allowed again. Two to eight weeks after the heat watch drinking, discharge, fever and lethargy (pyometra), six to nine weeks after for nesting and milk (false pregnancy).
See the vet immediately with excessive drinking and urinating, purulent or bloody discharge, vomiting, fever, a bloated belly or apathy. After a mating for a pregnancy check from day 25.
4. Anestrus: about 4 months
What happens: The ovaries rest and the uterus regenerates. This stage determines the interval between two heats: small breeds often four to six months, medium and large breeds about six to eight, giant breeds often only eight to twelve months.
How you recognise it: You don't. She behaves as usual and males show no interest.
What you can do: Anything. A good time for training class, holidays and a vet check. If spaying is planned, now is the time: at least two to three months after the heat, not during a false pregnancy. More under When to spay?
See the vet if the heat stays away for clearly more than a year or a dog has never been in heat by two years of age.
The stages at a glance
| Stage | Duration | Fertile? | Visible? |
|---|---|---|---|
| Proestrus | about 9 days (3 to 17) | no | yes: bleeding, swelling |
| Estrus | about 9 days (3 to 21) | yes | yes: lighter discharge, standing |
| Diestrus | about 9 weeks (60 to 90 days) | first 1 to 2 days | no |
| Anestrus | about 4 months (2 to 10) | no | no |
Lunella shows these four stages as a ring and a bar on the home screen, with the current day and the texts for each stage. You only enter when the heat starts, when she stands and when it is over.
This article does not replace veterinary advice. If your dog shows signs of illness, see your vet.
