How Long Do Female Dogs Bleed?

Bleeding during a female dog’s heat is part of her reproductive cycle and involves mucus and blood from the vulva as hormone-driven changes progress.

What is bleeding during a dog’s heat

Bleeding during heat is the visible vulvar discharge that accompanies the reproductive phases of an intact female dog and reflects normal, cyclical changes in the uterus and vagina. The canine estrous cycle is composed of four stages—proestrus, estrus, diestrus, and anestrus—and the type and timing of discharge vary with those stages ^[1].

Bleeding most commonly begins in proestrus, when rising estrogen levels increase blood flow to the vulvar tissues and cause the endometrium and vaginal mucosa to produce bloody, mucous discharge; this bleeding during heat most commonly lasts about 7 to 10 days ^[1]. Individual dogs can fall well outside that average: some show only a few days of staining while others may show intermittent spotting for longer periods, with typical ranges reported from roughly 4 days up to about 21 days ^[1].

The phenomenon applies to intact (unneutered) female dogs; spayed females do not experience proestrus or estrus bleeding because the ovaries that drive the hormonal cycle are removed. Most intact females experience their first heat between about 6 and 24 months of age ^[2], and breed size shifts that timing: smaller-breed dogs commonly cycle earlier (often by 6 to 9 months), whereas many large or giant-breed dogs may not have a first heat until 12 to 24 months ^[2].

Distinguishing heat-related bleeding from other causes is important: bleeding tied to the cycle is predictable with behavioral and physical signs of proestrus or estrus, whereas bleeding from trauma, coagulopathy, infection, or tumors may be sudden, heavy, malodorous, accompanied by systemic illness, or unrelated to the timing of the reproductive cycle; when bleeding deviates from expected patterns, veterinary evaluation is indicated ^[1].

Bleeding during a female dog’s heat is part of her reproductive cycle and involves mucus and blood from the vulva as hormone-driven changes progress.

What is bleeding during a dog’s heat

Bleeding during heat is the visible vulvar discharge that accompanies the reproductive phases of an intact female dog and reflects normal, cyclical changes in the uterus and vagina. The canine estrous cycle is composed of four stages—proestrus, estrus, diestrus, and anestrus—and the type and timing of discharge vary with those stages ^[1].

Bleeding most commonly begins in proestrus, when rising estrogen levels increase blood flow to the vulvar tissues and cause the endometrium and vaginal mucosa to produce bloody, mucous discharge; this bleeding during heat most commonly lasts about 7 to 10 days ^[1]. Individual dogs can fall well outside that average: some show only a few days of staining while others may show intermittent spotting for longer periods, with typical ranges reported from roughly 4 days up to about 21 days ^[1].

The phenomenon applies to intact (unneutered) female dogs; spayed females do not experience proestrus or estrus bleeding because the ovaries that drive the hormonal cycle are removed. Most intact females experience their first heat between about 6 and 24 months of age ^[2], and breed size shifts that timing: smaller-breed dogs commonly cycle earlier (often by 6 to 9 months), whereas many large or giant-breed dogs may not have a first heat until 12 to 24 months ^[2].

Distinguishing heat-related bleeding from other causes is important: bleeding tied to the cycle is predictable with behavioral and physical signs of proestrus or estrus, whereas bleeding from trauma, coagulopathy, infection, or tumors may be sudden, heavy, malodorous, accompanied by systemic illness, or unrelated to the timing of the reproductive cycle; when bleeding deviates from expected patterns, veterinary evaluation is indicated ^[1].

Typical duration and timeline

Most intact female dogs show a recognizable timeline of bleeding that follows the proestrus → estrus → diestrus progression and gives owners a predictable pattern to watch for ^[3].

On average, the visible bloody discharge of proestrus lasts about 7 to 10 days, and many textbooks and clinic guidelines report a common overall bleeding window of roughly 4 to 21 days across different individuals ^[1]. Proestrus (the phase with the heaviest bloody discharge) commonly lasts about 7 to 10 days, followed by estrus (when bleeding typically diminishes and the fertile window occurs) for about 5 to 9 days, and then diestrus, during which bleeding generally stops and the luteal phase continues for roughly 60 to 90 days before anestrus ^[1].

Variability is common: some dogs have shorter cycles with only a few days of notable staining while others may show spotting that begins early or lingers at low volume for several weeks, and owners should expect individual differences rather than a single fixed number for every dog ^[3].

Heat cycle stages and bleeding patterns

Mapping the reproductive stages to typical bleeding patterns helps owners recognize what is expected at each step and when changes are unusual ^[4].

Typical bleeding appearance and timing during the canine estrous stages

Stage	Typical bleeding/appearance	Typical duration	Key behavioral signs
Proestrus	Bloody, mucous discharge that may be moderate	About 7–10 days [1]	Attraction of males, female generally not receptive
Estrus	Reduced bleeding or pinkish spotting; mucus increases	About 5–9 days; fertile window within this phase [1]	Receptive to males, flagging tail behavior
Diestrus	Bleeding stops; discharge wanes to clear/mucoid	Approximately 60–90 days luteal phase [1]	Pregnancy or false pregnancy signs may appear
Anestrus	No vaginal bleeding or reproductive discharge	Several months until next proestrus; variable timing [3]	Normal baseline behavior, reproductive rest

Normal color, volume, and consistency

Normal estrous discharge typically progresses from bright red to pink and then brown as blood ages and mucus predominates, and owners commonly see this color shift over the course of days to a couple of weeks ^[5].

Volume varies by dog: many show only spotting or light staining, while others have a light flow; a practical clinical estimate used by clinics is that typical heat-related discharge is often less than about 1 ounce (≈30 mL) per day rather than large-volume hemorrhage ^[2]. Consistency also changes from bloody to more mucous as estrus approaches, with mucus increasing during the fertile window ^[1].

Changes that may still be normal include brief heavier days early in proestrus or intermittent spotting at the tail end of estrus, whereas sudden heavy flows, very dark foul-smelling discharge, persistent large clots, or any discharge accompanied by systemic illness should prompt veterinary assessment ^[3].

Factors that influence bleeding length

Several biological and external variables cause the duration and character of bleeding to differ between dogs, so the same calendar of days will not apply exactly to every individual ^[1].

Age and whether it is a first heat matter: first heats are often more irregular, and many dogs have more predictable cycle lengths after two or three cycles ^[2]. Breed and size influence timing: smaller breeds often cycle earlier and sometimes more frequently, while large and giant breeds tend to have later onset and may have different inter-estrus intervals ^[2].

Individual hormonal variation, concurrent health problems (for example, endocrine disease or uterine infection), medications, or stress can also lengthen or shorten observable bleeding, and clinicians consider those factors when a dog’s bleeding pattern departs from expectations ^[4].

Red flags: when bleeding is abnormal

Owners should seek veterinary care for bleeding that is unusually prolonged, heavy, malodorous, or accompanied by systemic signs such as fever, weakness, or loss of appetite ^[6].

Specifically, bleeding that continues beyond about 21 days, sudden heavy bleeding that soaks bedding or a diaper rapidly, discharge with a foul smell or pus, visible large clots, or signs of anemia (pale gums, lethargy) are considered red flags that need prompt veterinary evaluation ^[1].

If bleeding occurs in a spayed dog, or if there is blood in the urine, persistent straining, or any systemic illness, these situations are not typical of heat and warrant immediate examination ^[3].

Common medical causes of abnormal bleeding

Several pathological conditions can cause excessive or prolonged vaginal bleeding rather than normal estrous spotting, and clinicians evaluate for these when bleeding falls outside typical patterns ^[7].

Pyometra, a uterine infection that commonly develops in diestrus weeks after estrus, is a frequent serious cause; pyometra classically occurs several weeks (often 4 to 8 weeks) after estrus and can produce purulent, malodorous discharge and systemic illness ^[3]. Vaginal or uterine masses (tumors or polyps), ovarian cysts, coagulopathies (inherited or acquired bleeding disorders), trauma, and foreign bodies are other important differentials that veterinarians consider ^[4].

Veterinary diagnostic approach

Vets use a combination of history, physical examination, and targeted tests to determine whether bleeding is part of a normal cycle or due to disease ^[4].

Typical diagnostics include a reproductive-focused physical exam and detailed history of timing and behavior, vaginal cytology to stage the cycle, and vaginal or uterine culture if infection is suspected ^[4]. Ultrasound imaging of the uterus and ovaries is commonly used to detect pyometra, masses, or cysts, and abdominal radiographs may be helpful in some cases ^[1].

Blood work—complete blood count (CBC) and serum chemistry—and coagulation testing are used when systemic illness or a bleeding disorder is suspected, and urinalysis can help rule in or out concurrent urinary tract disease ^[4].

At-home care and monitoring during bleeding

Owners can take practical steps to keep their dog comfortable and to monitor for concerning changes while the dog is in heat ^[2].

Hygiene measures include using dog-specific diapers or absorbent bedding and changing soiled diapers every 4 to 6 hours to reduce skin irritation and infection risk, plus gentle cleaning of the vulvar area with warm water and a soft cloth as needed ^[2]. Owners should prevent unwanted mating and supervise outdoor time carefully during proestrus and estrus because fertile mating generally occurs during estrus ^[1].

Monitor behavior, appetite, and the amount and smell of discharge daily; keeping a simple log of start date, color changes, and any unusual signs makes veterinary discussions clearer if a problem arises ^[4].

Treatment options and prevention (including spaying)

Treatment for abnormal bleeding depends on the cause and ranges from medical therapy for infection to surgical intervention; spaying is the definitive preventive option for heat-related cycles and many uterine diseases ^[3].

When infection such as pyometra is diagnosed, medical stabilization often includes intravenous fluids and broad-spectrum antibiotics, and many cases require surgical ovariohysterectomy; antibiotics alone are sometimes used in carefully selected patients but carry a higher recurrence risk ^[3]. For coagulopathies or systemic causes of bleeding, treatment targets the underlying disorder and may involve blood product support, clotting-factor therapy, or discontinuation of causative drugs as appropriate ^[4].

Elective ovariohysterectomy (spay) removes the ovaries and uterus and therefore prevents future heats and estrous bleeding; veterinary and public-health organizations commonly recommend spaying for owners not planning breeding because it eliminates heat-related bleeding and greatly reduces or eliminates the risk of pyometra and certain reproductive tumors ^[1]. Timing and individual medical considerations influence when a spay is safest, and veterinarians discuss optimal timing based on breed, age, and health status ^[3].

Sources

• merckvetmanual.com — small animal reproductive and emergency medicine content.
• vcahospitals.com — clinical client-facing guidance and breed/age timing.
• avma.org — professional guidance on reproductive health and spaying.
• aaha.org — diagnostic and clinical practice recommendations.
• ncbi.nlm.nih.gov — peer-reviewed studies and review articles on estrous timing and variability.
• merckvetmanual.com — guidance on red flags and emergency signs.
• avma.org — information on common reproductive pathologies like pyometra.