A dog in heat typically lasts about 2 to 4 weeks (14 to 21 days) on average. This period is the fertile phase when the dog can become pregnant

. The heat cycle has distinct phases:

• Proestrus: Lasts about 7 to 10 days, during which the vulva swells and there is blood-tinged discharge. The dog is not receptive to males yet

• Estrus: The actual "heat" phase lasts around 3 to 21 days (average 9 days), when the female is receptive to mating and most fertile

• Diestrus and Anestrus: Follow the heat phase and involve recovery and rest before the next cycle

Bleeding usually occurs during the first half of the heat cycle, typically lasting 7 to 10 days, but not throughout the entire heat period

. Most dogs go into heat about twice a year, roughly every 6 to 7 months, though this can vary by breed, size, and individual factors

. In summary:

• Heat duration: about 2-4 weeks
• Bleeding duration: about 7-10 days
• Frequency: about twice per year (every 6-7 months)

This cycle continues throughout the dog's life unless spayed