6 Signs That Your Dog Is in Heat

Canine estrus happens in the spring and fall

A black and a white labrador playing in backyard

Stefan Cristian Cioata/ Getty Images

If you're the loving owner of a female dog that has not been spayed, you definitely need to know the signs of your dog in heat. A female dog of reproductive age that has not been spayed is called a bitch. Canine estrus, or heat, will occur seasonally in the spring and fall. A dog that is spayed cannot go into heat since the dog's uterus and ovaries have been surgically removed, leaving the canine sterile.

Your Dog's First Heat

The age of a dog's first heat varies greatly. The average age for the first heat is 6 months, but anytime within the first year is normal. The timing differs depending on the individual dog, the breed, and the size of the dog. The first heat is usually earlier for small dogs than large dogs. Unlike the signs you see when a cat is in heat, dogs are typically messier and do not appear to be in "pain" during the heat cycle as cats sometimes do.

Signs That Your Dog Is in Heat

The more aware you are of your dog's cycle, the more prepared you will be for any physical changes and mess that may occur from the dog's estrus cycle. These six signs are what to look out for: 

  1. Swollen vulva. This non-painful swelling typically occurs a few days before any discharge or bleeding will occur.
  2. Bleeding. A bloody discharge from your dog is usually the first sign of heat you will notice. Discharge consistency and color varies during the cycle. It can range from bloody to clear or straw-colored. The amount of discharge varies from slight to heavy, depending on the dog, as does the length of time discharge occurs.
  3. Mounting behavior. Your dog may try to mount other dogs, objects, or your leg. During heat, she might tolerate being mounted by other dogs, which can be a change in normal behavior.
  4. Licking genital area. This is your dog's attempt at keeping the area clean. Depending on the dog, this may or may not be successful. Some dogs need to wear diapers during the heat cycle to prevent soiling bedding and the house.
  5. Agitated, nervous, or nesting behavior. Your dog might appear more anxious or clingy than usual while in heat. Additionally, she might collect toys and stuffed animals and place them in her sleeping area.
  1. Urinating more often. Frequent urination is a way of marking and letting other dogs know she is in heat. If you suspect urinary problems, which are also indicated by excessive licking of the genital area or frequent urination, it is important to take your dog to the veterinarian as soon as possible.
illustration of signs your dog is in heat
Illustration: Vin Ganapathy. © The Spruce, 2018

The Four Stages of Heat

There are four stages of the canine estrus cycle. Each has it's own characteristics and lasts for different amounts of time. 

  1. Proestrus. The sign of the first phase is vaginal discharge from your dog. Males canines will be attracted to female dogs but the females will be unwilling to mate. This phase can last for 4 to 20 days.
  2. Estrus. The dog will have a swollen vulva and yellowish vaginal discharge. During estrus is when mating occurs. This second phase can last for 5 to 13 days.
  3. Metestrus (or Diestrus).This is the time after estrus or mating and can last for 60 to 90 days. If the female dog is pregnant, most canine pregnancies last around 60 days. 
  4. Anestrus. This is the period of sexual and hormonal inactivity between estrus phases and will last for 2 to 3 months. If not spayed, the cycle will then begin again. 

Specific timing will vary with each dog and during each phase of the canine estrus cycle. Spaying is the best way to prevent pregnancy and can be done as early as four months of age. It is surgery that will prevent your dog from getting pregnant. The spay surgery removes both the ovaries and the uterus. It is a very common surgical procedure and can be done by a veterinarian or a pet clinic. If you have any questions about your dog's estrus cycle or see any worrisome behavior, speak to your veterinarian right away. 

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.