For an unspayed female dog, a heat cycle can bring changes in behavior, vulvar swelling and vaginal discharge. Timing and intensity vary from dog to dog, so there is no reliable single calendar date that predicts every cycle. Tracking the beginning of each episode can help with future discussions with your veterinarian.
Common signs of a heat cycle
Owners may notice swelling around the vulva, bloody or pink discharge, more frequent urination and increased interest from male dogs. Some females become more affectionate, restless or less interested in routine activity. As the cycle progresses, discharge and receptivity can change. A dog may still be fertile when bleeding has become lighter or less obvious.
Prevent unintended breeding
Keep an in-season dog securely supervised, away from intact male dogs, and use a leash outdoors. A fence or diaper alone cannot prevent mating. Ask your veterinarian about spaying timing based on breed, age, health, and individual circumstances if you do not plan to breed.
What is not simply a normal heat symptom?
Very foul-smelling or pus-like discharge, severe lethargy, vomiting, painful abdominal swelling or increased thirst after a heat cycle can be warning signs of pyometra or another serious condition. Pyometra is an infection of the uterus that may be life-threatening and needs urgent veterinary care. Not every discharge in an intact female is heat-related.
When to speak to a veterinarian
Contact the clinic if cycles seem unusually frequent, absent, prolonged or dramatically different from prior patterns. Mention pregnancy possibility and any medications. Take notes about when swelling or discharge began, but do not attempt home hormonal treatments. If the dog is weak, collapsed or visibly ill, seek emergency care.
Further reading
Merck Veterinary Manual, canine reproductive cycles and pyometra; general veterinary warning signs.
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.