How long is a female dog in heat?

When a female dog goes into heat, timing affects more than breeding: it changes daily routines, risks, and the way you manage other dogs and people in your home. Knowing what to expect saves stress, prevents accidental litters, and helps you spot when something is wrong.

What a female dog’s heat cycle means for you and your pet

Breeding decisions are the most obvious reason to pay attention. If you plan to breed, knowing the heat window helps choose the right mating days and decide whether to consult a reproduction specialist. For most owners, the practical priorities are preventing unwanted pregnancies and avoiding encounters with intact males—both of which often require temporary changes to how a dog is exercised and contained.

Behavior and health monitoring is another reason. Heat can bring visible changes—bleeding, swollen vulva, increased mounting or clinginess—that are usually normal but may mask early illness. Tracking cycles lets you notice patterns or departures from what’s typical for your dog, which can prompt timely veterinary checks.

Finally, logistics matter. Boarding facilities, dog walkers, and dog parks may have specific rules for females in heat; if you know your dog’s cycle you can plan boarding, socialization, and walks to keep her safe and comfortable.

How long a typical heat cycle lasts — what to expect

Most female dogs are in heat for roughly 2 to 4 weeks from the start of proestrus through the end of estrus, with the most fertile window usually lasting several days within that span. The cycle is commonly described in stages: proestrus (often 7–10 days, when bleeding and swelling begin), estrus (usually 5–10 days, when the female will accept males and ovulation occurs), and diestrus (about 60–90 days of hormonal change following estrus). Between cycles, many bitches come into heat every 4 to 8 months, though smaller breeds often cycle more frequently and large breeds sometimes less often. Individual dogs and particular breeds can vary enough that the best guide is the pattern you observe in your own dog over time.

Hormones and stages: the biology of canine estrus explained

The heat cycle is driven by shifting reproductive hormones: estrogen tends to rise as the body prepares for mating, then progesterone rises around ovulation and during diestrus. Those hormonal shifts are likely linked to both the visible signs you notice (bleeding, swelling, behavioral changes) and the internal fertility window. Ovulation in dogs does not always match the first day of outward receptivity, so the days a female appears willing to mate and the days she is actually fertile may overlap but are not always identical.

Timing the cycle: when the first heat usually occurs and how often it repeats

Age of first heat varies with size and breed. I typically see small-breed dogs enter puberty as early as 5–6 months, while many large-breed dogs don’t have a first heat until 12–18 months. Normal frequency tends to be roughly twice a year, but seasonality is not as strict in domestic dogs as in wild canids; some bitches show mild seasonal patterns while others cycle year-round.

Health, body condition, and neuter status affect timing. Underweight dogs or those with endocrine disorders may have irregular cycles. Certain breeds—Basenjis, for example—are known for less frequent cycles, while small terriers may cycle more often. Chronic illness, stress, or poor nutrition can shift timing or make signs subtler.

Recognizing problems: warning signs and health risks to watch for

Most heat cycles are routine, but some signs suggest a problem. Abnormal bleeding—for example, heavy, prolonged bleeding beyond the typical 2–4-week window—or a sudden foul smell to vaginal discharge may suggest infection. If discharge becomes thick, pus-like, or bloody in a way that’s different from the usual spotting, that is a reason to check with your veterinarian.

Pyometra, an infection of the uterus, is one serious risk in intact females as they age. Early signs can be vague—lethargy, decreased appetite, increased thirst or urination—or more obvious, such as fever and a swollen abdomen. If a dog shows a combination of fever, vomiting, weakness, or marked changes in drinking and urination while in the weeks after estrus, seek veterinary care promptly because pyometra can become life-threatening.

Excessive lethargy, persistent fever, or signs that the dog is in pain are urgent. Likewise, any sudden behavioral collapse, difficulty breathing, or collapse should be treated as an emergency.

Owner checklist: practical steps to take during each stage of heat

1. Record the dates: Note the first day you see blood or swelling and write down changes in behavior. Keep a simple calendar or an app entry so you can see intervals and any pattern over months.
2. Limit contact: From the day bleeding begins until the vulva appears back to normal, prevent unplanned mating by supervising outdoor time, using secure fencing and leashed walks, and avoiding dog parks or off-leash areas.
3. Provide comfort and hygiene: Use washable dog pants or disposable pads to protect furniture. Check and gently clean the vulva area only if needed—excessive cleaning can irritate sensitive tissue. Change bedding frequently and use enzymatic cleaners for any soiled areas.
4. Adjust exercise and outings: Keep walks shorter and to quieter routes, and avoid areas where intact males frequent. Consider timed potty breaks in a securely fenced yard rather than long neighborhood strolls during peak receptivity.
5. Decide on spaying or breeding: If you are not planning to breed, discuss spaying with your veterinarian. Spaying eliminates future heats and reduces certain health risks, though timing and the dog’s health should be considered.
6. Call your veterinarian if things change: Contact your clinic if bleeding is heavy or prolonged, discharge smells bad or looks infected, the dog shows fever, vomiting, marked lethargy, or other worrying signs.

Keeping training and home life on track while she’s in heat

Containment and movement flow in the home needs attention. Create routes so your dog can move between rooms without passing through common areas where other dogs congregate. If you have multiple dogs, separate intact males and females during her cycle; I often recommend using baby gates and closed doors to limit visual and scent contact.

Walking strategy matters. Short, predictable walks on a secure leash and harness reduce the chance of an excited male suddenly breaking off to pursue. Avoid dog parks and off-leash spaces until at least a week after estrus ends and hormones have settled.

Behavioral changes—increased clinginess, restlessness, or mounting—can often be managed with short training sessions, distraction, and predictable routines. Reward calm behavior, use brief redirections when she mounts or solicits attention, and provide safe chew or enrichment to occupy her during times of restlessness. If anxiety is severe, discuss short-term veterinary options with your vet.

Prepare other pets and family members. Young children should be supervised and taught not to approach the genital area; other pets may need brief separation to prevent stress-related fights or unwanted mating attempts.

Essential products and supplies to have on hand

Dog diapers and reusable pants: Choose a well-fitting pant rather than loose sanitary products; they stay in place better and reduce skin rubbing. Measure waist and rear girth to pick the right size, and wash reusable pants on a gentle cycle. If using disposable pads, secure them so the dog cannot chew and ingest them.

Secure leash and harness: A strong, well-fitting harness gives you better control than a collar during sudden attempts to bolt. Consider a short hands-free leash for steadying the dog without excess slack. For travel, use a properly sized crate so the dog has a predictable, calm space.

Cleaning supplies and bedding: Enzymatic cleaners are useful for biological stains and odors; keep spare bedding available so you can change a crate or couch cover frequently. Have gloves and mild, dog-safe wipes on hand for spot cleaning the dog if needed—avoid harsh soaps near the vulva.

Health-tracking tools: A simple calendar, notebook, or phone app to log cycle start and end dates, behavior changes, and any treatments will help you and your vet spot trends. If you plan to breed, keep a folder with health clearances, vaccine records, and notes on previous cycles.

References and trusted resources

• Merck Veterinary Manual: “Reproduction in the Dog and Cat” — Merck & Co., Inc., Merck Veterinary Manual. (https://www.merckvetmanual.com/)
• AVMA: “Spaying and Neutering — Guidance for Pet Owners” — American Veterinary Medical Association resources on reproductive health and timing.
• Johnston, S.D.; Root Kustritz, M.V.; Olson, P.N.S. Canine and Feline Theriogenology, 2nd Edition — Saunders (comprehensive textbook on small-animal reproduction).
• Cornell University College of Veterinary Medicine: “Canine Reproduction and Neonatology” client resources and breeder guidelines.
• Concannon, P.W. and England, G. — Selected review articles in Theriogenology and Journal of Small Animal Practice on estrous cycle timing and ovulation in the bitch.