If you're new to owning an unspayed female dog, you'll definitely want to learn how often a dog comes into heat. Most dogs go into heat twice a year, although you may see differences among breeds and individual dogs based on their size, age, and other factors. Find out when to expect your dog's heat cycle so you're prepared and can plan her spay surgery accordingly.
Typical Dog Heat Cycle: The 411
The canine heat cycle is complex, but here are the fast facts every dog owner should know:
- The onset of heat cycles usually begins when female dogs 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 21 days.
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 number of times a dog will go into heat per year often depends on their size:
- Small breed dogs, such as Chihuahuas and Maltese, can go into heat twice a year but sometimes as many as three times.
- Medium-sized dogs, such as American pit bull terriers and Labrador retrievers, will go into heat about twice a year.
- Large breed dogs, such as German shepherd dogs and Bernese mountain dogs, generally go into heat twice a year but sometimes only once a year.
- Giant breed dogs, such as great danes, may only go into heat every 12 to 18 months.
Heat Cycles and Dog Breed
A few breeds, including basenjis and Tibetan mastiffs, go into heat only once a year despite their size.
Heat Cycles After a Pregnancy
A dog's regular heat cycle might be delayed a bit following a pregnancy. Most will resume cycling about four to six months after delivery once they are fully recovered from raising their litters.
Infertile Heat Cycles
Although cycling every four months or roughly four times a year can be normal for some small breed dogs, it's usually abnormal and equally rare in other dogs. These cycles are usually infertile.
Incomplete Heat Cycles
In even rarer cases, some female dogs 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 dog to experience this irregularity during her first cycle or two until she establishes a regular pattern.
Heat Cycles in Senior Dogs
Dogs have the potential to have heat cycles throughout their entire lives, unlike human females who enter 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 dog with a well-established pattern of heat cycles suddenly misses a cycle or two, it's a good precaution to make your veterinarian aware of the situation. Sometimes, a physical malady can affect how often a female dog comes into heat, and it's always better to consult your veterinarian 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 in order to ensure her health.
No First Heat Cycle
In some cases, a dog 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 she 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 have an unspayed dog, it's important to be aware of when her heat cycles will occur so you can care for her properly. Most veterinarians prefer to spay a dog before her first heat cycle, but this can vary based on your dog. Still, it's a general consensus that spay surgeries during a heat cycle are more difficult, complicated, and time-consuming, so if your dog is currently in heat, it's often best to wait until about a month or two after her cycle finishes.
