A female dog

Question: My female puppy is in heat. How long will it last?

My 6-month-old new female puppy is in heat. How long will this last? How do I deal with this besides crating or just leaving her in a confined area?



Dear Kathy,

Thank you for writing with your question about your puppy. These days, so many female dogs are already spayed when people adopt them, it’s not uncommon for people to be confused about a dog’s heat cycles.

The medical term for a dog being “in heat” is being in estrus. Female pups usually experience a first estrous anywhere from six to twelve months of age. In addition to the estrus phase, there is a whole cycle that you should understand to be able to help your dog stay healthy.

The 4 Phases of the Canine Estrus Cycle:

  1. Proestrus: duration 7-12 days.
    This early phase is when you will see an enlarged vulva and possibly bloody vaginal discharge. It is during this phase that a female dog starts to attract male dogs. This is not the prime time for breeding, though. Although they’ll allow males to approach, females will not stand for mating during proestrus.
  2. Estrus: duration 7-9 days.
    Estrus is the fertile period. Vaginal discharge changes from bloody to straw-colored and vulvar swelling is still present. Females will stand for mating during this phase.
  3. Diestrus: duration about 65-90 days.
    Characterized by a discontinuation of vaginal discharge and unwillingness to stand for mating. This is the time that pups start to form if mating has taken place. If pregnant, diestrus lasts the length of gestation period–63-65 days. If the female dog is not pregnant, the duration of diestrus is 75-90 days. There are no outward signs of diestrus in non-pregnant dogs.
  4. Anestrus: duration from the end of diestrus to the beginning of next proestrus phase.
    Anestrus is the resting time for the reproductive tract. The dog will look and behave “normally” during anestrus.

The parts of the cycle that will be noticeable to you are proestrus and estrus. These phases are the equivalent of being “in heat.” The time from the beginning of proestrus to the end of estrus is about 21 days. Therefore, a female dog is in heat for around three weeks.  Most female dogs come into “heat” once or twice a year.

If you’re planning on breeding your female pup, it’s recommended to wait until she’s about two years old. This will allow her body to mature physically before asking it to undergo the stress of pregnancy and giving birth.

Male dogs can be extremely persistent when they smell a female dog in estrus. For this reason, you must watch your pup very closely at all times. Leaving her outdoors alone or anywhere near an intact male dog runs the risk of unwanted early pregnancy.

Another thing to keep in mind is that young pups often have unpredictable first estrus cycles. It’s not unusual for them to be in heat longer or shorter than usual. They may or may not pass blood, but they usually do have visible vulvar swelling. Some female dogs have changes in behavior during this time, too. They can be more irritable or more cuddly than usual.

You can use panties or diapers to contain excessive vaginal discharge. Several models are available and are well-tolerated by most dogs. These are not reliable for preventing mating so you still need to keep her away from males!

Give your girl a little extra attention and keep a close eye on her for safety. Most dogs come through the experience with little difficulty.


TB Thompson DVM

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