Dog Heat Cycle Tracker

The four phases of the heat cycle

Proestrus (days 1-9)

The cycle begins with vulvar swelling and bloody discharge. Female is attractive to males but rejects them. Estrogen levels rise. This is the "warning" phase before peak fertility.

Estrus (days 9-14)

True heat — the fertile window. Discharge lightens to straw-color, swelling reaches maximum, and the female actively seeks and accepts males. Ovulation typically occurs 2-3 days into this phase. For breeding, plan matings every 48 hours through the receptive window.

Diestrus (days 14-60)

Whether or not pregnancy occurred, hormones shift. If pregnant, gestation is 63 days from breeding (try the pregnancy calculator). If not pregnant, some females show pseudopregnancy signs — nesting, mothering toys, milk production. Usually resolves in 2-3 weeks.

Anestrus (days 60-180+)

Reproductive rest. The body resets for the next cycle. Length of anestrus determines the overall cycle interval — 4 months in small breeds, 6 months typical, up to 12 months in giants.

Tracking tips

• Mark the first day of bleeding as cycle day 1, not the day swelling starts.
• Record discharge color daily — bright red → straw-colored is the key transition signaling fertile window.
• Use diapers or doggy pants for around-the-house bleeding. Most dogs adjust quickly.
• Avoid dog parks during the entire 21 days of active heat — even after bleeding stops, hormone signals attract intact males.
• Keep records of 2-3 cycles to identify your dog\'s individual pattern. The first heat is often atypical.

Frequently asked questions

How often do dogs go into heat?

Most adult dogs cycle every 5-7 months, with 6 months as the median. Small breeds tend toward shorter cycles (every 4-5 months); large and giant breeds toward longer cycles (every 8-12 months). Cycles can also be irregular for the first 1-2 years after the first heat.

When is a female dog fertile?

Peak fertility is days 9-13 from the start of bleeding (proestrus). Ovulation typically occurs 2-3 days after bleeding lightens and the discharge turns from bright red to straw-colored. The fertile window is short — successful breeding usually requires multiple matings 48 hours apart.

What are the phases of a heat cycle?

Proestrus (days 1-9): bleeding, swelling of vulva, but female refuses males. Estrus (days 9-14): true heat, female accepts males, lighter discharge, fertile. Diestrus (days 14-60): cycle ending, may show signs of pseudopregnancy. Anestrus (days 60+): reproductive rest until next cycle.

When should I spay my dog?

Veterinary opinions vary. Traditionally spaying happens before the first heat (~6 months). Newer research suggests waiting until after the first heat for large/giant breeds to reduce orthopedic and certain cancer risks. Discuss timing with your vet — it depends on breed, lifestyle, and individual health.

Is the cycle irregular for puppies?

Yes — first heats often arrive between 6-15 months and the first 1-2 cycles can be irregular in length, intensity, and interval. After age 2, most dogs settle into a predictable pattern. Senior dogs (10+) may have longer intervals or "silent heats" with minimal external signs.