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How Often Does a Dog Go into Heat? Vet Reviewed Facts & FAQ

Grant Piper

By Grant Piper

Dog smells a dog in heat

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Dr. Paola Cuevas Photo

Reviewed & Fact-Checked By

Dr. Paola Cuevas

MVZ (Veterinarian)

The information is current and up-to-date in accordance with the latest veterinarian research.

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Many domesticated dogs in the Western world are spayed. A spay is a procedure that removes a dog’s ovaries and uterus, which prevents them from becoming pregnant. While most dogs are spayed (especially if you get them from a rescue or a shelter), not all dogs are. Dogs that are not spayed have the chance to go into heat. Going into heat is something that happens periodically when a dog experiences its estrus cycle. This is the only time that a dog is able to get pregnant. How often does a dog go into heat? It depends. Every dog is a little different.

Most dogs will go into heat every 6 months, but this interval is not the same for every dog. Some dogs have shorter or longer intervals. This brief guide will go over everything you need to know about a dog’s estrus cycle, including how often they occur, how long they last, how many days per year a dog will spend in heat, and more.

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Average Canine Estrus Cycle

Dogs go into heat every 6 months on average. That means that a typical female dog will go into heat one to two times per year. However, this can vary depending on your dog’s breed, health, and size. Large dogs typically go into heat once per year, while small dogs can go into heat three to four times per year.

Unlike other animals, birds, horses, and goats, dogs do not have a season that corresponds to their heat cycles. Other animals only go into heat during specific seasons. Dogs can go into heat at any point during the year. For example, if your dog has its first heat cycle in February, it will likely have its next heat cycle in August or September, regardless of the season.

Large Dogs

Large dogs have fewer heat cycles than small dogs. Large dog breeds such as Saint Bernards and Great Danes might only go into heat every 12 to 18 months. This can make it hard to breed large dogs, and you will get fewer litters per year than you would with a small dog.

Small Dogs

Small dogs can go into heat three or even four times per year. That means that small dogs go into heat every 3 to 4 months rather than every 6 months. This can make breeding small dogs more lucrative and more frequent than with larger dogs. It also means you will have to deal with your dog being in heat for many more days than with larger dogs which can be frustrating if you are not actively trying to breed your dog.

Dog sniffing dog in heat
Image Credit: atiger, Shutterstock

How Long Will Dogs Be in Heat?

Dogs typically remain in heat for 1 to 2 weeks at a time. Like the estrus cycle in general, this can vary from dog to dog and breed to breed. Some dogs might only be in heat for a few days, while other dogs could be in heat for 3 weeks or longer.

A heat cycle can last anywhere from 5 to 21 days.

Average Heat Days Per Year

The typical dog will go into heat twice per year for 10–15 days at a time. That means that an average dog will spend 20–30 days per year in heat. This can be much lower for large dogs (5–10 days) and much higher for small dogs (30–40 days.)

Average heat cycle: Every 6 months
Days per cycle: 7–15
Average days in heat per year: 14–28

These numbers are important for anyone who decides against spaying their dog. If you are planning to breed, it is important to know when your dog is in heat so you can make a breeding plan. Dogs are pregnant for about 9 weeks at a time. If you are not planning to breed, it is very important to know when your dog is in heat to prevent unwanted pregnancies and monitor for behavioral and physical changes.

When Will My Dog Start Going into Heat?

Dogs can start going into heat at around 1 year of age. However, at the beginning of their life, a dog’s estrus cycle can be sporadic rather than consistent. That means that most dogs do not settle into a regular cycle until they are 2 years old. From 1 year to 2 years of age, a dog’s heat cycle might only occur once per year or at irregular intervals.

jack russell in heat
Image Credit: Reshetnikov art, Shutterstock

Keeping Track

If you plan on keeping your female dog intact, it is a good idea to keep track of their heat cycles. This will give you valuable insight into your particular dog. While the average numbers tend to hold true for most breeds, every dog is a little different.

Keep track of when your dog goes into heat, and then make a note of how many days your dog remains in heat. If you keep these records for two or more years, you will start seeing a consistent pattern. These patterns will help you plan for the future and will give you a heads-up as to when your dog is likely to go into heat.

Remember, dogs will not start getting consistent heat cycles until at least 18 months of age, but it could also be later.

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Knowing when you can expect your dog to go into heat can be important information for dog breeders and regular pet owners alike. Most dogs will go into heat every 6 months or twice per year, but some dogs can go into heat more or less frequently, depending on their age and size. Dogs will typically spend 14 to 30 days per year in heat. These days will affect your dog’s overall health and behavior. This information is critical to people looking to breed their dog.


Featured Image Credit: sanjagrujic, Shutterstock

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