How Long Are Dogs in Heat?

You probably have some awkward questions when it comes to your dog getting her period such as how long are dogs in heat? Here’s your dog period guide!

You probably have some questions when it comes to your dog getting her period such as how long are dogs in heat? Here’s your dog period guide!

Dealing with a dog in heat can sometimes be a frustrating experience for owners who never had to deal with it before. To avoid any difficulties, there are many things to learn and apply to keep your female dog breed comfortable during her heat cycle.

When a female comes into heat or season, her body is preparing for mating and the possibility of producing a litter.

Generally, from around the age of 6 months old, a female dog will experience her first heat cycle. However, this depends on your dog’s size. Smaller dogs can go into heat as soon as they are 4-months old. On the other hand, this can take longer for larger breeds.

In this article we will explore the four stages of the estrous cycle and the symptoms associated with each stage.

4 Stages of the Dog Heat Cycle

The canine reproductive cycle is made up of 4 different stages.  These are proestrus, estrus, diestrus, and anestrus.

The Heat Cycle Stages in Dogs

1. Proestrus

This is the very beginning of a dog’s heat. Proestrus is the stage that most owners start noticing changes and when we say “the dog is in heat”.

During proestrus a dog probably can’t get pregnant, but there’s always a chance. Males will notice the female during this initial stage, but the female won’t be willing to mate just yet.

Pet parents should start keeping their dog inside and away from male dogs at this time.

2. Estrus

Once the bleeding stops, the second stage (estrus) of the dog heat cycle has begun. Many people make the mistake of thinking their dog’s estrus is done at this point, but this second stage is actually when your dog can become pregnant.

During this stage, she sometimes exhibits a behavior called “flagging.” This involves the female dog standing in one place, while at the same time, lifting her tail to allow the male to sniff her hind end.

Estrus is the stage when the female is receptive to the male. This lasts an additional 5 to 13 days.

Also, keep in mind that your dog can get very creative when she’s in heat. Always watch her and avoid walks during this time. Do not go near a strange male dog that is approaching her – they’re more aggressive and likely to bite when they want to mate.

3. Diestrus

This phase occurs directly after the “in heat” stage and lasts between 60 and 90 days, but don’t worry. At this point, the dog is no longer fertile.

Pet owners who didn’t want puppies can breathe a sigh of relief when diestrus starts. Their dogs will no longer be interested in running off to find potential mates or making overt and awkward advances toward male dogs.

4. Anestrus

The anestrus stage is the time when a dog is not in heat and behaves normally. During this time, there is no sexual or hormonal behavior. This phase can last for anywhere from 90 to 150 days before the next proestrus stage begins.

Signs a Dog Is in Heat

The first signs your dog is in heat are the swelling of her vulva and bright red bloody discharge. Typically bleeding is light during the first few days and grows a bit heavier mid-week. This is one of the best ways to spot the beginning of a dog heat cycle.

Swelling and bleeding are the most obvious physical signs that a dog is entering her heat cycle, but most pups also experience some behavioral changes.

A female dog that is in heat will often urinate more frequently than normal, or may develop marking behavior, in which she urinates small amounts on various objects either in the home or when out on a walk.

Most dogs will tuck their tail when other pups approach to guard their vulvas. Some dogs also experience changes in appetite.

How Often Do Dogs Come In Heat?

A dog’s heat cycle recurs roughly every 6 months for unspayed female dogs until 8 to 10 years of age. Each heat cycle lasts around 18 days, generally anywhere from 2 to 3 weeks.

Just like people, dogs can also have irregular cycles, especially when first reaching puberty. It can take a female dog up to 2 years to develop a regular heat cycle.

As your dog gets older, the frequency of her seasons may slow down. However, she will be going into heat for her whole life.


Heat cycles are a natural part of every female’s life. If you desire to breed your dog, make sure you’re willing to go through the necessary work of breeding and wait for three heat cycles (or eighteen months).

If you don’t want to breed, the best way to prevent your dog from becoming pregnant is to have her surgically sterilized before she has her first estrous cycle. Additionally, spaying prevents uterine infections and ovarian and uterine cancer.

There are other options for dog birth control, but spaying is the most common and usually the most recommended method.