How Long Do Dogs Stay In Heat — Explained

Key Takeaways

Dogs typically stay in heat for 14-21 days on average, though this can range from 12-28 days depending on breed and individual factors

The heat cycle consists of four distinct phases: proestrus (7-10 days), estrus (5-9 days), diestrus (2-3 months), and anestrus (4-5 months)

Female dogs usually go into heat twice a year, approximately every 6 months, starting from 6-24 months of age

During heat, dogs experience physical signs like vulva swelling, bloody discharge, and behavioral changes including increased urination and restlessness

Spaying is the most effective way to prevent heat cycles and associated complications like unwanted pregnancy and pyometra

You notice your female dog acting differently—restless, urinating more frequently, and there’s that telltale bloody discharge. Your dog is in heat, and you’re wondering exactly how long this will last. Understanding your dog’s heat cycle helps you provide better care, prevent unwanted pregnancy, and recognize when something might be wrong. By learning how long do dogs stay in heat on average and based on their breed and size can help keep you alert to common signs of issues during the canine estrous cycle.

Most dogs stay in heat for 14-21 days, though individual variation means some female dogs experience cycles as short as 12 days or as long as 28 days. This timeframe represents the visible portion of your dog’s reproductive cycle or the dog estrous cycles when bleeding and behavioral changes occur. The duration depends on factors like breed size, age, and individual genetics.

Let’s break down everything you need to know about canine heat cycles, from timing to management strategies that keep both you and your dog comfortable during this natural process.

The term “heat” and the dog period questions answered above also specifically refers to your dog’s fertile period when she can become pregnant. However, the female dog’s reproductive cycle extends well beyond these visible weeks, encompassing four complete stages that span several months.

Smaller breeds like Chihuahuas and Yorkshire Terriers often have shorter heat cycles, typically lasting 12-18 days. Larger breeds such as German Shepherds and Great Danes may experience longer cycles, extending 18-24 days or more. Your dog’s breed, combined with her individual genetics, plays a significant role in determining her specific cycle length.

First heat cycles tend to be irregular and often shorter than subsequent ones. Young female dogs may experience their initial heat for only 7-10 days, with cycles becoming more consistent and longer as they reach physical maturity. Don’t be surprised if your dog’s cycle length varies slightly between seasons—this variation is completely normal.

Phase	Duration	Key Signs	Fertility Status
Proestrus	7-10 days	Bloody discharge, vulva swelling, attracts males but won’t mate	Not fertile
Estrus	5-9 days	Discharge lightens, receptive to mating, ovulation occurs	Fertile
Diestrus	60-90 days	High progesterone, possible pregnancy or false pregnancy	Not fertile
Anestrus	4-5 months	Reproductive rest, hormone levels low	Not fertile

Phase

Duration

Key Signs

Fertility Status

Proestrus

7-10 days

Bloody discharge, vulva swelling, attracts males but won’t mate

Not fertile

Estrus

5-9 days

Discharge lightens, receptive to mating, ovulation occurs

Fertile

Diestrus

60-90 days

High progesterone, possible pregnancy or false pregnancy

Not fertile

Anestrus

4-5 months

Reproductive rest, hormone levels low

Not fertile

Proestrus Phase (7-10 days)

The proestrus phase marks the beginning of your dog’s visible heat cycle. During these initial 7-10 days, you’ll notice the first signs that alert most pet parents: a swollen vulva and bloody vaginal discharge. Your female dog will attract male dogs during this phase, but she won’t allow mating attempts.

Estrogen levels peak during proestrus, causing the physical changes you observe. The bloody discharge starts light and gradually increases, while the vulva continues swelling. Behaviorally, your dog may seem restless, urinate more frequently, and show increased interest in her surroundings.

Male dogs will be intensely interested in your female dog during this phase, following her scent trail and attempting to approach. However, your dog will typically rebuff these advances with snapping, growling, or simply moving away. This rejection behavior is completely normal and indicates her hormones haven’t shifted to the receptive stage yet.

Estrus Phase (5-9 days)

The estrus phase represents true “standing heat”—the period when your female dog becomes receptive to male dogs and can conceive. This phase typically lasts 5-9 days, though some dogs may be receptive for as little as 3 days or as long as 2 weeks.

During estrus, the bloody discharge changes to a straw-colored or clear fluid, though some dogs continue bleeding lightly throughout. The key behavioral change is your dog’s willingness to accept male dogs, often demonstrated by “flagging”—moving her tail to one side when approached by a male.

Ovulation occurs approximately 2 days into the estrus phase, though the exact timing varies among individual dogs. Your dog remains fertile for several days after ovulation, creating a window of opportunity for pregnancy. Progesterone levels begin rising during this phase, preparing the uterus for potential pregnancy.

If you’re trying to prevent pregnancy, extra supervision during estrus is crucial. Even the most well-behaved female dog may escape or allow mating during this hormonally-driven phase.

Diestrus Phase (60-90 days)

Following estrus, your dog enters diestrus regardless of whether she became pregnant. This phase lasts approximately 60-90 days and is characterized by high progesterone levels that prepare and maintain the uterine lining.

During diestrus, the bloody discharge stops and the swollen vulva returns to normal size. Your female dog will no longer accept male dogs and may show aggression toward their advances. Progesterone levels peak around 2-3 weeks after ovulation, then gradually decline over the following weeks.

If your dog is carrying puppies, you’ll notice mammary gland enlargement, weight gain, and behavioral changes as pregnancy progresses. Non-pregnant dogs may experience false pregnancy symptoms due to similar hormonal changes, including mammary development, nesting behavior, and even lactation.

The high progesterone levels during diestrus create an increased risk for pyometra, a serious uterine infection that requires immediate veterinary attention. This risk exists whether your dog became pregnant or not, making it important to monitor for signs like lethargy, excessive thirst, or unusual discharge.

Anestrus Phase (4-5 months)

Anestrus represents the reproductive “rest” phase between heat cycles. During these 4-5 months, hormone levels remain low, allowing your dog’s reproductive system to recover and prepare for the next cycle.

You’ll notice your female dog returns to her normal behavior during anestrus—no special interest from male dogs, no discharge, and stable energy levels. This phase provides the perfect opportunity for spaying if you choose not to breed your dog, as surgical risks are lowest when hormone levels are minimal.

The length of anestrus varies significantly among breeds and individual dogs. Smaller breeds may have shorter anestrus periods, cycling twice a year or even three times annually. Larger breeds often have extended anestrus phases, with some cycling only once per year.

When Dogs First Go Into Heat

Female dogs typically experience their first heat cycle between 6-24 months of age, with significant variation based on breed size and individual development. Small dogs like Toy Poodles often go into heat as early as 6 months, while larger breeds such as the Tibetan Mastiff may not experience their first cycle until 18-24 months.

The relationship between reaching adult size and sexual maturity explains this timing variation. Smaller breeds reach physical maturity faster, triggering earlier reproductive cycles. Larger breeds need more time to develop their skeletal structure and overall body mass before hormonal systems activate reproductive functions.

Your dog’s first heat cycle may be shorter and less obvious than subsequent cycles. Many pet parents miss the first season entirely because the physical signs are barely noticeable—minimal discharge, slight vulva swelling, and subtle behavioral changes. First cycles often last only 7-14 days compared to the typical 14-21 days of mature cycles.

Responsible breeders recommend waiting until at least the second heat cycle before considering breeding, even if your dog experiences her first heat early. Physical and emotional maturity continues developing well after the first cycle, and breeding too young can create complications for both mother and puppies.

Monitor your young female dog carefully after 6 months of age, regardless of breed. Early spaying (before the first heat) provides maximum health benefits, but the window for this preventive measure closes once hormonal cycling begins.

Frequency of Heat Cycles

Most dogs go into heat twice a year, approximately every 6 months, establishing a predictable pattern once reproductive maturity is reached. This frequency remains relatively consistent throughout your dog’s life, though cycles may become less frequent or irregular as she ages.

However, breed exceptions exist to this standard pattern. Basenjis typically cycle only once per year, usually in the fall. Some primitive breeds and larger dogs like Great Danes may also follow annual cycles rather than the standard twice-yearly pattern. These variations are normal for specific breeds and don’t indicate health problems.

Individual dogs may experience slight variations in cycle timing, with intervals ranging from 4-8 months between heat cycles. Stress, illness, nutrition, and environmental factors can influence cycle regularity. Young dogs often take several cycles to establish a consistent pattern, while older dogs may gradually extend the time between cycles.

Unlike humans, dogs don’t experience menopause. Female dogs continue cycling throughout their lives, though the fertility rate decreases with age and cycles may become less regular. This continued cycling means the health risks associated with repeated estrous cycles—including mammary cancer and pyometra—accumulate over time.

Keep detailed records of your dog’s heat cycles, noting start dates, duration, and any unusual symptoms. This information helps your veterinarian assess reproductive health and can be crucial for breeding decisions or identifying potential problems.

Physical Signs Throughout the Cycle

Swollen vulva (begins in proestrus, peaks in estrus)

Bloody vaginal discharge (heavy initially, lightening during estrus)

Increased urination frequency

Mammary gland enlargement (subtle in most dogs)

Appetite changes (may increase or decrease)

Slight temperature elevation

Behavioral Changes You’ll Notice

Increased restlessness and attention-seeking

More frequent marking and scent investigation

Changes in social behavior with other dogs

Possible aggression toward female dogs

Attraction to male dogs during estrus

Nesting behavior in some dogs

The progression of bloody discharge provides a reliable indicator of cycle phases. Initial discharge appears bright red and may be quite heavy, requiring doggie diapers or careful management of your dog’s environment. As estrus approaches, discharge typically lightens to pink or straw-colored, though some dogs maintain darker bleeding throughout.

Male dogs will detect your female dog’s heat cycle long before obvious signs appear, thanks to pheromone release that occurs days before visible symptoms. You may notice male dogs in your neighborhood showing increased interest in your yard or becoming more attentive during walks, even when you haven’t observed any physical changes yet.

Some dogs experience minimal discharge or other subtle signs, making heat cycles difficult to detect. These “silent heats” are more common in certain breeds and young dogs experiencing their first few cycles. Regular veterinary check-ups can help identify these subtle cycles through examination and hormone testing.

Managing a Dog in Heat

Successfully managing your dog during heat requires preparation, patience, and consistent attention to prevent unwanted breeding while keeping your home clean and your dog comfortable.

Home Management Strategies

Start by restricting your dog’s access to carpeted areas and furniture you want to protect. Many pet parents find doggie diapers helpful, though not all dogs tolerate wearing them initially. Introduce protective clothing gradually with treats and positive reinforcement. Washable blankets and towels in your dog’s favorite resting spots provide easy cleanup options.

For dogs who won’t wear diapers, frequent cleaning becomes essential. Keep cleaning supplies readily available and clean accidents immediately to prevent staining and odor. Some owners find that limiting their dog to tile or hardwood areas during the heaviest bleeding days simplifies maintenance.

Exercise and Outdoor Safety

Exercise needs don’t disappear during heat, but outdoor activities require careful planning. Avoid dog parks and areas with high concentrations of other dogs. Male dogs can detect a female in heat from considerable distances, potentially creating situations that are difficult to manage even in fenced areas.

Consider shorter, more frequent walks in your immediate neighborhood where you can maintain better control. A fenced in yard provides the safest option for outdoor time, though you’ll need extra supervision to prevent neighborhood dogs from approaching your fence line. Some determined unneutered male dogs may attempt to jump fences or dig underneath to reach a female in heat.

Preventing Unwanted Breeding

Never leave your female dog unsupervised outdoors during heat, even in a secure yard. Dogs in heat have been known to escape from areas they’ve never left before, driven by hormonal changes that affect judgment and behavior. Male dogs may also become more creative about accessing your property.

If you live in a multi-dog household with non neutered dogs, temporary separation becomes necessary. Even dogs who normally get along well may need to be kept apart during the female’s receptive phase. Consider boarding one dog or using baby gates to create separate living spaces within your home.

Comfort and Care

Some dogs experience discomfort during heat, similar to menstrual cramps in humans. Provide extra comfortable bedding and consider a warm compress for dogs showing signs of discomfort. However, most dogs don’t appear to experience significant pain during normal heat cycles.

Monitor your dog’s appetite and water intake, as these may fluctuate during hormonal changes. Maintain regular feeding schedules and ensure fresh water is always available. Some dogs become pickier eaters during heat, while others may show increased appetite.

Contact your veterinarian if you notice signs of illness including lethargy, loss of appetite, excessive thirst, vomiting, or unusual discharge with a foul odor. While heat cycles are normal, complications like pyometra can develop and require immediate treatment.

Pyometra Risk

Pyometra, a serious uterine infection, represents the most significant health risk for unspayed female dogs. This condition can develop during or after any heat cycle, with risk increasing with age and the number of cycles experienced. High progesterone levels during diestrus create ideal conditions for bacterial growth within the uterus.

Watch for warning signs including excessive thirst, frequent urination, lethargy, loss of appetite, vomiting, and unusual vaginal discharge with a foul odor. Pyometra can be life-threatening without prompt treatment, typically requiring emergency spaying and supportive care.

False Pregnancy

Many female dogs experience false pregnancy (pseudopregnancy) following heat cycles, regardless of whether mating occurred. Hormonal changes during diestrus can trigger pregnancy-like symptoms including mammary enlargement, nesting behavior, and even milk production.

While false pregnancy usually resolves without treatment, severe cases may require veterinary intervention. Dogs experiencing pronounced false pregnancy symptoms may benefit from medication to reduce prolactin levels and alleviate discomfort.

Mammary Cancer Risks

Repeated heat cycles increase mammary cancer risk in female dogs. Dogs spayed before their first heat have less than 0.5% risk of developing mammary tumors. This risk increases to 8% after the first heat and 26% after the second heat cycle.

Regular mammary examinations during routine veterinary visits help detect tumors early when treatment is most successful. Monthly home examinations can also help identify changes between professional check-ups.

Breeding Considerations

If you plan to breed your dog, timing is crucial for successful conception. Optimal breeding typically occurs 10-14 days after the onset of heat, though individual variation means veterinary monitoring provides the most accurate timing guidance.

Responsible breeders use progesterone testing, vaginal cytology, and behavioral observation to determine the best breeding window. These scientific methods provide much more accurate timing than relying solely on physical signs or calendar counting.

Breeding during the first heat cycle is not recommended, even for dogs who reach sexual maturity early. Physical and emotional maturity continues developing well past the onset of reproductive cycling, and early breeding can compromise both maternal and puppy health.

Spaying as Prevention

Spaying (ovariohysterectomy) permanently prevents heat cycles and eliminates the associated health risks, making it the most effective long-term management strategy for non-breeding dogs. The procedure removes both ovaries and the uterus, preventing hormone production that drives reproductive cycling.

Health Benefits of Spaying

The health advantages of spaying extend well beyond preventing unwanted pregnancy. Spayed dogs cannot develop pyometra, ovarian cancer, or uterine cancer. Early spaying (before the first heat) provides maximum protection against mammary cancer, reducing risk to nearly zero.

Spaying also eliminates the stress and discomfort associated with heat cycles, creating a more consistent quality of life for your dog. The behavioral changes that accompany heat—restlessness, increased urination, and attraction to male dogs—disappear permanently after spaying.

Optimal Timing

Veterinary medicine traditionally recommended spaying before the first heat cycle to maximize health benefits. However, recent research suggests that timing may vary based on breed size and individual factors. Larger breeds may benefit from waiting until physical maturity, while smaller breeds can safely be spayed earlier.

Discuss optimal timing with your veterinarian, considering your dog’s breed, size, lifestyle, and individual health factors. The decision should balance cancer prevention benefits with potential orthopedic considerations in large breeds.

Surgical Considerations

Spaying during heat increases surgical complexity and bleeding risk, leading most veterinarians to recommend waiting until anestrus when possible. However, emergency spaying may be necessary if pyometra develops during or shortly after a heat cycle.

Recovery from spaying typically takes 10-14 days, during which activity restriction and careful monitoring prevent complications. Most dogs return to normal activity levels within two weeks, with complete healing occurring over the following month.

Post-Surgical Care

Following spay surgery, monitor your dog for signs of complications including excessive swelling, bleeding, or changes in appetite and energy level. Keep the incision clean and dry, and prevent licking or chewing with an Elizabethan collar if necessary.

Weight management becomes more important after spaying, as metabolic changes may increase the tendency toward weight gain. Adjust feeding amounts as needed and maintain regular exercise to prevent obesity-related health problems.

FAQ

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Can dogs get pregnant during their first heat cycle?

Yes, dogs can get pregnant during their first heat cycle if they mate during the fertile period. However, breeding during the first heat is not recommended because young dogs haven’t reached full physical and emotional maturity. Most responsible breeders wait until at least the second heat cycle, and many prefer waiting until 18-24 months of age for larger breeds to ensure proper development.

Do dogs experience pain or cramps during heat like humans do?

Most dogs don’t appear to experience significant pain during heat cycles, unlike human menstruation. While some dogs may seem slightly uncomfortable or restless, severe pain is not normal and should prompt a veterinary examination. If your dog shows signs of distress, lethargy, or appears to be in pain during her heat cycle, contact your veterinarian to rule out complications like pyometra.

How can I tell when my dog’s heat cycle is ending?

The heat cycle is ending when the bloody discharge stops completely, the swollen vulva returns to normal size, and your dog no longer attracts or accepts male dogs. The discharge typically lightens in color and decreases in volume before stopping entirely. Most dogs show clear behavioral changes as well—they’ll reject male attention and return to their normal personality and energy levels.

Is it normal for my dog’s heat cycle length to vary between cycles?

Yes, it’s completely normal for heat cycle length to vary slightly between cycles. Individual dogs may experience cycles ranging from 12-28 days, and the same dog might have a 16-day cycle followed by a 21-day cycle. Factors like stress, age, health status, and environmental changes can influence cycle length. However, dramatic changes in cycle length or timing should be discussed with your veterinarian.

What should I do if my dog’s heat cycle lasts longer than 28 days?

If your dog’s heat cycle extends beyond 28 days, contact your veterinarian for evaluation. While some individual variation is normal, prolonged cycles may indicate hormonal imbalances, ovarian cysts, or other reproductive disorders. Your vet may recommend hormone testing, ultrasound examination, or other diagnostic procedures to determine the cause and appropriate treatment.