Care & how-to
Dog in Heat: Signs, How Long It Lasts and How to Cope
A dog in heat is a female dog in the fertile part of her reproductive cycle, usually about nine days of vulvar swelling, bloody discharge and strong interest from male dogs. Most dogs go through it about twice a year. She can get pregnant at any point, so supervision matters most. Some owners use dog diapers to protect floors during the cycle.
By Matt GarnettUpdated November 14, 20264 min read2 sources
What being in heat means
Being in heat, also called being in season, is the estrus stage of the canine reproductive cycle, when a female dog is receptive to mating. VCA Animal Hospitals says estrus lasts about 9 days on average, with a range of 2 to 24 days. The American Kennel Club divides the full cycle into four stages: proestrus, estrus, diestrus and anestrus.
Proestrus and estrus are each about 9 days in the AKC's description, though either can range from 3 to 21 days. Diestrus then lasts around 60 days and anestrus roughly four to six months, so the visible heat is only a small part of the cycle.
Signs your dog is in heat
VCA says vulvar swelling is usually the earliest sign, though it is not always obvious. Bloody discharge is often what owners notice first, and it may not appear until several days in. It begins very bloody and thins to watery and pink as the cycle goes on.
Other changes include more frequent urination, or small amounts of urine left on walks and around the home, which carries scent that can draw males from a distance. The AKC adds tail flagging when she is ready to mate, and behavior changes. Some dogs turn withdrawn or spooky, some more clingy, and some short-tempered with other dogs. A few lose their appetite.
How often it happens and when it starts
VCA says most dogs cycle twice a year, while small breeds may cycle three times a year and giant breeds about once. The AKC notes the Basenji is a well-known exception, with one cycle a year. Early cycles can be irregular, and VCA says it may take up to two years for them to settle into a pattern.
The first heat arrives around six months on average. The AKC says toy breeds may start as early as four or five months, while giant breeds may not cycle until about two years old. Dogs do not go through menopause, so heats continue for life even if they get quieter with age.
Keeping her safe from unplanned pregnancy
VCA says a dog can become pregnant at any point during estrus and that sperm can survive about a week in the reproductive tract. Pregnancy can also happen without a visible tie. Keep her on a leash outdoors, and do not leave her tied up in the yard, because the AKC warns that intact males can follow her scent home. Even a fenced yard is not fully safe.
If you think she has been mated by accident, VCA says to contact a veterinarian as soon as possible, because options exist but they carry risks and need your vet's supervision. Spaying before the first cycle is the most reliable way to prevent pregnancy, according to VCA, and your vet can advise on the best timing for your dog's size and breed.
Managing the mess and your dog's comfort
Keep her routine steady and offer comfort if she wants it, but give her space if she is withdrawn. Washable bedding and easy-to-clean floors help, and the AKC notes that dog diapers can protect furniture and floors. It stresses they do not prevent pregnancy.
If you want to try them, our dog diapers collection shows what is available. Change any diaper often, wipe the area gently and check the skin, since constant moisture can irritate it. Walks can continue, but only on a leash and away from places where male dogs gather.
Laying a washable pee pad or an old dog blanket over her favorite resting spot makes cleanup easier during the cycle.
When to call your vet
The AKC says pyometra, a uterine infection, is rare but potentially life-threatening. It is most common in older unspayed females and typically shows up four weeks to four months after a heat. Increased thirst, more urination, a change in appetite and low energy are the warning signs it lists, and it says to contact a vet promptly if you see them.
Also call your vet if bleeding seems unusually heavy or long, if your dog stops eating or seems unwell, or if you are unsure whether what you are seeing is a normal heat. Ask about spaying at the same visit, since the AKC says it is typically done after sexual maturity and at least one heat, and early spaying carries trade-offs that depend on the breed.
This page is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your pet.
Common questions
How long does a dog stay in heat?
VCA says estrus usually lasts about 9 days, with a range of 2 to 24 days. The AKC describes the bloody proestrus and the fertile estrus as roughly 9 days each, with the whole cycle lasting much longer.
How often do dogs go into heat?
Most dogs cycle about twice a year. VCA says small breeds may cycle three times a year and giant breeds about once, and early cycles can be irregular for up to two years.
Can a dog get pregnant at any time during heat?
Yes. VCA says a dog can get pregnant at any point during estrus because sperm can survive about a week, and pregnancy can happen even without a tie, so keep her supervised.
Do dog diapers stop a dog getting pregnant?
No. The AKC says diapers can protect floors and furniture during a heat but do not prevent pregnancy. Leash walks and close supervision away from intact males are what protect her.
When should I call the vet about my dog in heat?
Call if you suspect an accidental mating, if bleeding seems heavy or long, or if she has more thirst, more urination or low energy in the weeks after a heat, which can signal a uterine infection.
Sources we checked
This guide is general information, not veterinary advice. If your pet is unwell or injured, contact your veterinarian.
