How Often Dogs Typically Come Into Heat

Updated June 19, 2019
Two Collies

If you're new to owning an unspayed female dog, you will definitely want to learn how often a dog comes into heat. You can expect most dogs to go into heat twice a year although you may see differences among breeds and individual dogs.

The Typical Dog Heat Cycle

The onset of heat cycles usually begins when most bitches reach the age of six months, although with larger breed dogs the first cycle may not occur until they are one to two years old. The actual cycle runs approximately two to four weeks with three being the average. The average interval between cycles is six months but can vary from four to 18 months depending on the dog. One of the most recognizable signs of the heat cycle is bleeding from the vulva, which commonly lasts about four to 15 days but can last up to eight more days.

The Dog Heat Season

Although the heat cycle, or estrus, is referred to as a dog going "into season" there is no specific month or time of the year when dogs will go into heat. A dog can go into heat virtually any month of the year, although there are a few breeds that tend to go into heat only in the spring.

Variations in the Dog Heat Cycle

There are several reasons that a dog may go into heat more or less often than the average time intervals. It helps to know the signs of a dog going into heat if this is your first time, such as behavior changes, bleeding, and swelling of the vulva.

Heat Cycles and Dog Size

The amount of times a dog will go into heat per year often depends on their size:

Heat Cycles and Dog Breed

A few breeds go into heat only once a year despite their size. Basenjis, Tibetan Mastiffs and sledding dogs such as Malamutes often only go into heat in the spring. Wolf hybrid dogs may also only go into heat once a year in the spring season.

Heat Cycles After a Pregnancy

A dog's regular heat cycle might be delayed a bit following a pregnancy. Most bitches will resume cycling about four to six months after delivery once they are fully recovered from raising their litters.

Golden Retriever bitch with her litter

Infertile Heat Cycles

Some bitches fall into a pattern of cycling every four months or roughly four times a year, although this is rare. At least one of these cycles is usually infertile. This means that ovulation does not occur even if the bitch gives signs of being willing to breed.

Incomplete Heat Cycles

In even rarer cases, some bitches will begin a cycle only to have it end prematurely. Then the owner finds the dog in heat again after two months. This irregular heat cycle pattern is sometimes referred to as a "split cycle," and it's not unusual for a young bitch to experience this irregularity during her first cycle or two until she establishes a regular pattern.

Heat Cycles in Senior Dogs

Bitches have the potential to have heat cycles throughout their entire lives, unlike a human female who enters menopause. It is normal for senior dogs, however, to have heat cycles grow farther apart as they age and develop health problems.

Irregular Heat Cycles

If a bitch with a well-established pattern of heat cycles suddenly misses a cycle or two, it's a good precaution to make your vet aware of the situation. Sometimes a physical malady can affect how often a bitch comes into heat, and it's always better to consult your vet sooner rather than later. Sometimes simple stress or a nutritional deficiency can delay the heat cycle, and that situation is often easily resolved. In other cases, it may even become necessary to spay the bitch in order to ensure her health.

No First Heat Cycle

In some cases, a bitch may reach past the age when she should have had a heat cycle yet has not had one yet. Veterinarians usually are not concerned until a bitch reaches beyond two years old without ever having had an obvious cycle. At that point, a vet should examine her to determine why she doesn't cycle and whether that might be detrimental to her health depending on the cause.

Dealing With Your Dog's Heat Cycles

If you intend to have an unspayed bitch, it's important to be aware of when her heat cycles will occur so you can care for her properly. One way to get an idea of how often you can expect your dog to cycle is to find out how often her own mother cycled. This trait often runs the same within family lines, although there are always exceptions. You can also use a heat cycle calculator once she's gone into heat once to estimate her future cycles.

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How Often Dogs Typically Come Into Heat