When do dogs go into heat?

HotbotBy HotBotUpdated: July 2, 2024

Understanding the Canine Estrous Cycle

The canine estrous cycle, commonly referred to as "going into heat," is a natural part of a female dog's reproductive process. This cycle signifies that the dog is fertile and can mate. Understanding the stages and timing of the estrous cycle is crucial for dog owners, breeders, and veterinarians.

Typical Age for First Heat

Female dogs (also known as bitches) typically experience their first heat cycle between six months and two years of age. However, this can vary considerably based on the breed and individual dog. Small breeds often mature faster and may go into heat as early as six months, while larger breeds might not experience their first cycle until they are 18 to 24 months old.

The Four Stages of the Estrous Cycle

The canine estrous cycle consists of four distinct stages:


Proestrus is the initial stage, lasting around 7 to 10 days. During this period, the female dog's body begins to prepare for potential mating. Signs include:

  • Slight swelling of the vulva
  • Bloody vaginal discharge
  • Increased attention from male dogs, although the female will not yet be receptive


Estrus follows proestrus and typically lasts from 5 to 14 days. This is the stage where the female is fertile and receptive to mating. Key indicators include:

  • Clear or straw-colored vaginal discharge
  • Softened and enlarged vulva
  • Behavioral changes such as being more affectionate or restless
  • Actively seeking out male dogs and allowing mating


Diestrus is the period following estrus, lasting about 60 to 90 days if the dog does not become pregnant. During this phase:

  • The vulva returns to its normal size
  • Discharge ceases
  • The body either begins to return to a normal state or supports pregnancy


Anestrus is the final stage, a resting phase that lasts about 4 to 5 months. During anestrus:

  • The reproductive system is inactive
  • There are no outward signs of hormonal activity

Frequency of Heat Cycles

Most female dogs go into heat approximately every six months, although this can vary. Smaller breeds may cycle more frequently, sometimes every four months, while larger breeds may only cycle once a year. It's important to monitor your dog's cycles to understand her specific pattern.

Signs and Symptoms of Heat

Recognizing when your dog is in heat is essential for managing her health and behavior. Common signs include:

  • Swollen vulva
  • Bleeding or discharge
  • Increased urination
  • Behavioral changes like restlessness, aggression, or clinginess
  • Attraction to male dogs

Managing a Dog in Heat

Managing a dog in heat requires extra care to prevent unwanted pregnancies and manage behavioral changes. Tips include:

  • Keeping her indoors or supervised at all times
  • Using dog diapers to manage discharge
  • Maintaining a regular routine to reduce stress
  • Providing extra attention and comfort

Health Considerations

The estrous cycle can impact a dog's health in several ways. Unspayed female dogs are at risk for conditions such as pyometra (a serious uterine infection) and mammary tumors. Spaying your dog can prevent these risks and eliminate the heat cycle.

Spaying and Its Impact

Spaying, or ovariohysterectomy, involves the surgical removal of a dog's ovaries and uterus. This procedure:

  • Eliminates the heat cycle
  • Prevents unwanted pregnancies
  • Reduces the risk of certain health issues
  • Can have behavioral benefits

Breeding Considerations

If you plan to breed your dog, understanding her heat cycle is crucial. Consulting with a veterinarian or a professional breeder can provide guidance on the optimal timing for mating and ensuring the health of both the mother and puppies.

Rarely Known Details

There are some lesser-known aspects of the canine heat cycle:

  • Silent heats: Some dogs may go through a heat cycle without noticeable signs, known as a "silent heat."
  • Split heats: Occasionally, a dog may start a heat cycle, stop, and then resume. This is more common in young dogs.
  • False pregnancies: Hormonal changes can cause a dog to exhibit signs of pregnancy even if she is not pregnant.

Tracking and Monitoring

Keeping a record of your dog's heat cycles can help in identifying any irregularities and planning for breeding, spaying, or general care. Apps and journals can be useful tools for tracking these cycles.

Understanding the intricacies of the canine estrous cycle is essential for responsible dog ownership. The timing, signs, and management of a dog in heat can vary widely, requiring attentive care and knowledge.

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