How Long Do Dogs Stay in Heat?

How long do dogs stay in heat? Well, you may be surprised to find that there is no simple answer.

There are many factors that affect the canine estrous cycle such as breed, age, health and size of the dog.

On average, a female dog is in heat for about 18 to 21 days twice a year. Typically, small breeds mature and experience earlier estrous cycles, while larger breeds, which mature more slowly, experience later cycles.

Because of this slower maturity, large breeds may only have one estrus cycle (heat) per year.

Here is a plain English explanation of common jargon used to describe dogs and the estrous cycle:

• Males are dogs. Once they father a litter, they are called sires.
• After females deliver a litter, they are referred to as dams.
• Progeny are pups.
• Proestrus is the time prior to estrus.
• Estrus is the egg production and ovulation period.
• Diestrus is the period of time following estrus.
• Anestrus is the period of time between estrus cycles.
• Proetrus and estrus are the follicular phase. This is when the egg forms and ovulation occurs.
• Diestrus and anetrus are the luteal phase. Simply, these refer to the days past ovulation and prior to the next estrous cycle.

During proestrus, the female does not allow a dog to mount or mate, but she does exhibit signs of sexual readiness. The vulvar area (genitals) swell and may be sensitive to the touch and there might be discharge, spotting, or bleeding. These are signs of a dog in heat.

The proestrus lasts approximately nine days in the average dog. Females in proestrus attract males but will not mate and there is little danger of pregnancy.

In this stage of the heat cycle in dogs, the female wants to mate and seeks a male. Males will be trying to reach her so the need for protection is greatest in this stage.

Confine the female inside the house as dogs are cunning when a female is in heat and can mate through fences and other obstacles. A crate is necessary to seclude and protect her if there are any male dogs in the household.

If she cannot be confined and protected from males, owners may want to consider boarding her for the average nine-day length of her season.

In diestrus, there may be some spotting or discharge, but the genital swelling goes down.

Males may try to mount, as the female is still secreting hormones, but she will not allow them.

This stage of the estrous cycle lasts for about 60 days.

This is a period of sexual inactivity and lasts about 200 days.

Most females are comfortable during this lull and require no special care.

For most breeds, females have two heats per year and these last about two to three weeks.

The size of the dog is one influencing factor that determines when the animal is sexually mature.

UCDavis, School of Veterinary Medicine, “Manage Reproduction”

University of Georgia, “The Canine Estrous Cycle: Staging Using Vaginal Cytological Examination,” Valerie R. Beimborn, DVM, Heather L. Tarpley, DVM, Perry J. Bain, DVM, PhD., Kenneth S. Latimer, DVM, PhD., 2003