At What Age Does a Dog Get Its Period?

When a female dog reaches puberty, she'll have her first estrous cycle. Generally, a dog experiences her first heat around 6 months of age; however, timing can vary widely according to a dog's size and breed. If you aren't interested in breeding Lady, it's fine to spay her before she's experienced her first cycle.

  1. The Estrous Cycle

    • A female dog has a reproductive or estrous cycle that consists of four stages: anestrus, proestrus, estrus and diestrus. Anestrus lasts three to five months and is a time of rest. Lady won't be interested in mating, nor will male dogs be attracted to her. Proestrus is a short stage, ranging from three to 17 days when males are interested in her, though she's still not welcoming suitors. Lady's attitude changes during estrus, which lasts from three to 21 days. Estrus is when she can get pregnant; if she becomes pregnant, she'll spend the next two months in diestrus, preparing for birth. If not, she's still in diestrus, and though her progesterone is elevated, she's not pregnant.

    Estrus Timing

    • When Lady reaches puberty, she'll experience her first estrus. It's a guess as to when exactly when she'll experience her first heat. As a rule, small-breed and smallish medium-size dogs tend to have their first heat at an earlier age, around 6 months. Large- and giant-breed dogs often don't come into heat until they're 18 to 24 months of age.

    Signs of Estrus

    • If Lady seems a little undone, she may be in her heat cycle. A female dog can be more alert or easily distracted than usual. She may also pee more often. You might notice her "period" as a blood tinged discharge during the first few days; the amount varies for each dog. About a week or so into her cycle, the discharge will change to a watery, pinkish-red discharge. This is about the time she can become pregnant because it's often when she begins ovulating. If you're interested in breeding Lady, consider the Louisiana State University Veterinary Medicine website's warning against breeding a dog during her first heat.

    Unique Dog, Unique Cycles

    • If Lady's like most dogs, she'll come into heat twice a year, about every six months. Small dogs may experience three heat cycles a year, compared with giant breeds who may go into heat only once every 12 to 18 months. Unlike cats, there's no seasonality to a dog's cycle -- it may take two years for Lady's cycle to become regular. The ASPCA recommends spaying your female dog to help protect against breast cancer and other reproductive diseases. As well, it takes the burden off animal shelters who contend with unwanted puppies and dogs.