6 Signs That Your Dog Is in Heat

Estrus Happens in Spring, Fall

A dog cools off in front of an electric fan
Kei Uesugi / 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 being in heat. A female dog of reproductive age who has not been spayed is called a bitch. (Yes, really.) They will go into heat, technically called estrus, seasonally, in the spring and fall. A dog that is spayed cannot go into heat since the uterus and ovaries have been surgically removed.

The age of a dog when she experiences her first heat is highly variable; the average is 6 months, but it varies from 6 to 12 or more months of age, depending on the individual and the breed and size of the dog. The first heat is earlier for small breeds than large breeds.

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

  • Swollen vulva: This non-painful swelling can be noticed a few days before any discharge or bleeding.
  • Bleeding: This is usually the first sign you will notice. Discharge varies during the cycle, and it is initially 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.
  • Mounting behavior:  She may try to mount other dogs, objects, or your leg. She might also stand to be mounted by other dogs.
  • Licking genital area: This may or may not keep the area clean. Some dogs need to wear diapers during the heat cycle to prevent soiling bedding and the house. ​
  • Agitated, nervous, or nesting behavior: Your dog might appear more anxious than usual or more clingy, or she might collect toys and stuffed animals in a sleeping area.
  • 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.

Reproductive Cycle of Dogs

These signs are a general overview and vary with each dog and during each phase of the canine estrus cycle. Spaying is the best way to prevent pregnancy if you don't want to breed your dog.

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