A dog’s heat usually lasts about 2 to 3 weeks, and most dogs come into heat about twice a year. Enter the first day of her last heat and this calculator shows where she is today, her likely fertile days, when the bleeding should stop and when the next heat is due. For a puppy, it shows when to expect her first heat.
How long does a dog stay in heat?
Most dogs show bloody discharge for 14 to 21 days, according to the Cornell University canine health center. VCA Animal Hospitals puts the fertile part (estrus) at about 9 days on average, but it can be as short as 2 days or as long as 24. So “about three weeks” is a fair answer for the whole heat, with plenty of normal variation.
The 4 stages of a dog’s heat cycle
| Stage | How long | What you’ll notice |
|---|---|---|
| Proestrus | 6 to 11 days on average | Swollen vulva and bloody discharge. Male dogs get very interested, but she won’t accept them yet. |
| Estrus | Usually 5 to 9 days, can be 1 to 20 | The discharge often turns lighter, pink or straw-colored. She may stand for a male. This is her fertile time. |
| Diestrus | About 2 to 3 months | Heat signs fade. Her hormones stay high for a while whether or not she’s pregnant. |
| Anestrus | About 1 to 6 months | Quiet resting phase until the next heat starts. |
Stage lengths: Cornell (proestrus, estrus) and the Merck Veterinary Manual (diestrus, anestrus). Merck notes that proestrus and estrus can each run anywhere from 3 days to 3 weeks.
How often do dogs go into heat?
Most dogs come into heat twice a year. Cornell gives a usual gap of 5 to 11 months. The Merck Veterinary Manual says the gap is normally 4 to 13 months, with 7 months the average. Size plays a part too. VCA notes that small dogs may cycle three times a year, while giant dogs may cycle only once. A few breeds, like the Basenji and Tibetan Mastiff, usually cycle just once a year.
The best guide is your own dog. Write down the first day of each heat. After two or three heats you’ll know her pattern, and you can put her usual gap into the calculator for a much better next-heat date.
When do dogs go into heat for the first time?
Usually somewhere between 6 and 24 months old. Smaller dogs tend to start earlier, often around 6 months. VCA says large and giant breeds may not have their first heat until 18 months to 2 years. Choose “She hasn’t had a heat yet” in the calculator to get the dates for your puppy.
Signs your dog is in heat
- A swollen vulva. VCA says this is usually the first sign, though it’s easy to miss.
- Bloody discharge that later becomes lighter and more watery.
- Peeing more often and marking with small amounts of urine.
- Male dogs suddenly following her around.
When is a dog most fertile?
During estrus, the second stage. VCA says ovulation usually happens around the time the discharge turns watery, and that’s when she’s most willing to breed. But she can get pregnant at any point during estrus. The exact day can only be found with progesterone blood tests from your vet, which is what breeders use. That’s why the calculator shows a window, not a single date.
Did she get bred? Our dog pregnancy calculator gives you the due date and a week-by-week calendar.
Frequently asked questions
How long does a dog’s period last?
Dogs don’t have periods the way people do, but the bleeding during heat usually lasts 14 to 21 days. Some dogs bleed very little and keep themselves clean, so it can be easy to miss.
Can a dog get pregnant on her first heat?
Yes. Any heat can lead to a pregnancy, including the first one. Keep her away from intact male dogs for the whole heat.
Can I spay my dog while she’s in heat?
Cornell suggests waiting about two months after the heat ends so her hormones settle down. Your vet will tell you the best timing for your dog.
Why is my dog’s heat irregular?
Some variation is normal, especially in the first year or two. The gap between heats can range from about 4 to 13 months. If her heats are very far apart, very long or very close together, ask your vet to check her.
Save to Pinterest