When Do Dogs Go Into Heat?

When Do Dogs Go Into Heat?

As a dedicated caregiver, understanding the lifecycle of your dog is paramount. It’s not just about feeding them, walking them, and playing fetch in the park — it’s about knowing what’s happening in their bodies too. One of the most crucial aspects you need to know about is their heat cycle. So, let’s dive into that subject right now.

What Exactly Is “Heat”?

“Heat” or “Estrus” is the stage in a female dog’s reproductive cycle during which she becomes receptive to mating with males. Dogs usually go into heat twice a year, but each dog differs in length of heat, discharge amount, and hormonal changes.

Interesting fact: smaller breeds may go into heat three times a year, while larger breeds usually only go into heat once a year.

When Do Dogs Go Into Heat for the First Time?

Your adorable little puppy isn’t going to stay little forever. As she grows, so does her reproductive system. The first heat usually occurs between 6-9 months for small breeds, and for large breeds, it could be as late as 18-24 months.

Here’s a simplified breakdown:

Breed Size Average Age at First Heat
Small 6-9 months
Medium 9-12 months
Large 12-18 months
Giant 18-24 months

Recognizing the Signs Your Dog Is in Heat

Knowing when your dog is in heat can help you prevent unwanted litters, as well as understand any behavior changes. Here are some signs:

  1. Swelling of the Vulva: This can begin a week before heat, continue throughout the cycle, and may not be noticeable in some dogs.
  2. Behavioral Changes: Your dog may become more affectionate, or on the flip side, more aggressive.
  3. Bleeding: This is usually the most notable sign. The bleeding can range from light spotting to heavier bleeding.

How Long Does a Dog Stay in Heat?

Typically, a dog stays in heat for 2-4 weeks. It starts with a week-long “Proestrus” stage, during which males are attracted to females, but she won’t reciprocate. Then comes “Estrus,” the 5-9 day period when the female is receptive to males. This is followed by “Diestrus,” which lasts 6-10 weeks.

How to Care for a Dog in Heat

Caring for your pet during this time can be challenging, but here are a few tips:

  • Keep her indoors: To avoid unwanted attention from male dogs.
  • Use doggy diapers: To handle the bleedings and spotting.
  • Give her extra attention: Changes in her hormones can lead to mood swings.


Q: Can a dog go into heat early?
A: Yes, some dogs can go into heat as early as four months old.

Q: How often will my dog go into heat?
A: Most dogs go into heat twice a year, but it can vary depending on the breed and individual dog.

Q: Can a spayed dog go into heat?
A: No, spaying a dog removes her uterus and ovaries, preventing her from going into heat.

Q: Should I breed my dog during her first heat?
A: It’s generally recommended to wait until at least her second heat to breed.

Remember, when it comes to your dog’s health, no question is too small or silly. It’s always better to ask and know than to wonder and worry. As caregivers, that’s our role: to ensure our pets are healthy, happy, and well-cared for, in every stage of their life.