Dogs In Heat: Timeline, Duration, and Symptoms

A female dog's heat (estrus) typically lasts 2 to 4 weeks and happens about twice a year. Bleeding is usually noticeable for the first 7 to 10 days, and — counterintuitively — a female is most fertile after the bleeding lightens, not during it. Most dogs have their first heat between 6 and 15 months of age, with small breeds cycling earlier and giant breeds sometimes not until 18–24 months.

Quick Answer: Heat unfolds in stages: about 9 days of swelling and bloody discharge when males are interested but she isn't (proestrus), then about 9 days of fertility with lighter, pinkish discharge when she'll accept a mate (estrus), then a return to normal. During the full 2–4 weeks, keep her leashed and separated from intact males — determined dogs are shockingly good at finding each other. If your intact female is also lethargic, drinking excessively, or has foul discharge weeks after a heat, call your vet immediately: those are signs of pyometra, a life-threatening uterine infection.

The 4 Stages of a Dog's Heat Cycle

The most common owner mistake lives in that second row: assuming the risky period ends when the bleeding does. It's the opposite — lighter discharge signals peak fertility, and supervision should tighten, not relax, in week two.

How Long Do Dogs Bleed in Heat?

Noticeable bleeding usually lasts about 7 to 10 days — roughly the first third to half of the full heat. Flow varies widely by dog and breed size; some fastidious dogs clean so thoroughly you'll barely notice, which is how "silent heats" sneak past owners. Dog diapers and washable blankets on furniture handle the housekeeping side.

How Often Do Dogs Go Into Heat?

Most females cycle roughly every 6 months, though every 4–12 months can be normal — small breeds may cycle three times a year, and giant breeds sometimes just once. Cycles are often irregular for the first year or two, then settle into a rhythm. Unlike humans, dogs don't menopause: intact females cycle for life, which is one reason senior intact females face rising risks of mammary tumors and pyometra, per the Merck Veterinary Manual's guidance on canine reproduction.

Signs Your Dog Is in Heat

• Swollen vulva and bloody discharge (the tell-tale pair)
• Frequent urination and increased marking on walks
• Restlessness, clinginess, or moodiness
• Excessive licking of the rear
• Tail "flagging" — held aside when touched near the hindquarters
• Intact males suddenly, intensely interested — often before you see anything else

How to Care for a Dog in Heat

• Leash-only outings for the full cycle. Even reliable recall fails against hormones — hers and theirs. Male dogs can detect a female in heat from remarkable distances.
• Secure the yard. Supervised bathroom breaks only; both escapes-out and visits-in happen more than owners expect.
• Manage the mess with dog diapers and washable covers.
• Offer comfort and routine — extra rest, patience with mood swings, and normal exercise in male-free areas.
• Keep meals consistent. Appetite often dips slightly during heat; a palatable, complete diet on a steady schedule helps — see our guide to feeding through appetite changes if she's turning meals down entirely.
• Know the emergency sign. Weeks after a heat, an intact female with lethargy, vomiting, heavy drinking, or pus-like discharge needs a vet now — pyometra is common in older intact females and fatal without treatment.

Should I Spay My Dog?

For most non-breeding dogs, yes — spaying eliminates heat cycles, unwanted pregnancy, and pyometra entirely, and reduces mammary tumor risk, which is why the American Veterinary Medical Association supports elective spay/neuter as a core preventive-care decision. Timing matters, though: for large breeds especially, recent research supports waiting until skeletal maturity, so the right age is an individual conversation with your vet, not a universal number.

The bottom line: Two to four weeks, twice a year, with fertility peaking just as the bleeding fades — manage those windows and you've managed the heat cycle. Consistent, quality nutrition supports her through the hormonal swings: Spot & Tango's recipes are formulated with pet nutritionists to meet AAFCO standards and portioned to her exact needs. Take the recipe quiz to build her plan.

Questions about feeding through life stages? Our customer care team is happy to help.

References:

• Merck Veterinary Manual: Breeding and Reproduction of Dogs. https://www.merckvetmanual.com/dog-owners/routine-care-and-breeding-of-dogs/breeding-and-reproduction-of-dogs
• AVMA: Spaying and Neutering. https://www.avma.org/resources-tools/pet-owners/petcare/spaying-and-neutering