A female dog typically bleeds for about 7 to 10 days during the proestrus phase of her heat cycle, which is roughly half of the total heat cycle duration. The entire heat cycle usually lasts between 2 to 4 weeks (14 to 21 days), with bleeding primarily occurring in the first half of this period
. Bleeding starts when the vulva swells and is usually blood-tinged discharge. The amount of bleeding can vary widely between dogs—some bleed heavily, while others have very light or barely noticeable bleeding, often influenced by how much they groom themselves
. The heat cycle has four stages:
- Proestrus (7-10 days): Bleeding starts, vulva swells, dog attracts males but is not receptive to mating.
- Estrus (5-10 days): Bleeding lessens or stops, dog is receptive to mating.
- Diestrus (10-140 days): Pregnancy or resting phase.
- Anestrus (about 6 months): Resting phase before the next cycle
In summary, bleeding during heat lasts about 7 to 10 days, within a total heat cycle of 2 to 4 weeks, though individual variation exists depending on the dog's size, breed, and behavior
