HEALTH
8 min
Dog Heat Cycle Explained: A Veterinarian’s Guide for Dog Parents
Veterinarian Dr. Rohit J explains the 4 stages of the dog heat cycle- what to expect, how to manage it, and when to spay for a smoother journey.
Dr Rohit Joseph
Veterinary Surgeon
Table of contents
What is ‘Heat Cycle’ in Dogs?
The heat cycle of dogs refers to a female dog’s reproductive cycle when she is fertile and capable of mating. Also known as the oestrous cycle, it consists of four stages, and each can impact their health and behaviour. Unlike humans, dogs don’t menstruate monthly- most go into heat twice a year, though this can vary by breed and size.
Understanding the heat cycle of dogs can help in managing behaviour, preventing unwanted pregnancies and deciding the right time to spay your female dog in heat.
Understanding the heat cycle of dogs can help in managing behaviour, preventing unwanted pregnancies and deciding the right time to spay your female dog in heat.
What Are the Four Stages of a Dog in Heat?
Unspayed female dogs typically go into heat every six to eight months, although this can vary depending on breed, age, and individual variation. The full cycle consists of four stages: Proestrus, Estrous, Dioestrus, and Anestrus. The most visibly noticeable period is Estrous, when a dog is fertile and may display dramatic behavioural and physical changes.
Let’s look at each of the four stages of the dog heat cycle in detail:
1) Proestrus Stage
Proestrus is the first stage of your dog’s heat cycle, when her body begins preparing for mating. One of the earliest signs is a bloody vaginal discharge, along with swelling of the vulva. This stage usually lasts 7 to 10 days, but it can vary between 3 to 21 days, depending on the dog.
Here are some common changes you may notice:
Hormonal Changes: A rise in oestrogen levels
Physical Signs:
2. Oestrous Stage: Ready for Mating/Fertile Period
The Oestrous stage is when your female dog is ready for mating and is the most fertile period of the dog heat cycle. This period lasts between 5 to 10 days. Here are some common changes you may notice:
Hormonal Changes: Oestrogen drops, progesterone rise
Physical Signs:
1) Proestrus Stage
Proestrus is the first stage of your dog’s heat cycle, when her body begins preparing for mating. One of the earliest signs is a bloody vaginal discharge, along with swelling of the vulva. This stage usually lasts 7 to 10 days, but it can vary between 3 to 21 days, depending on the dog.
Here are some common changes you may notice:
Hormonal Changes: A rise in oestrogen levels
Physical Signs:
- Bloody vaginal discharge (this is often the first visible sign)
- Swollen vulva
- Increased urination (marking behaviour)
- Attracts male dogs, but is not yet willing to mate
- May be more clingy or irritable than usual
- Increased interest in outdoor smells and other dogs
- Some females may start humping objects or other dogs
2. Oestrous Stage: Ready for Mating/Fertile Period
The Oestrous stage is when your female dog is ready for mating and is the most fertile period of the dog heat cycle. This period lasts between 5 to 10 days. Here are some common changes you may notice:
Hormonal Changes: Oestrogen drops, progesterone rise
Physical Signs:
- Discharge becomes lighter (pinkish or straw-coloured)
- Vulva remains swollen but softens
- “Flagging” behaviour - moves tail to the side to allow mating
- Becomes receptive to males and may seek them out
- Actively attempts to escape to reach male dogs
- May show roaming behaviour or restlessness
- Mounting or playful solicitation of other dogs
Normal vs. Swollen vulva
3. Dioestrus Stage
Dioestrus is the third stage of your dog’s heat cycle. It begins once she’s no longer fertile and has stopped accepting male attention. Her body now shifts from mating mode to a recovery or pseudo-pregnancy state. Even if she wasn’t bred, her hormones behave as if she might be pregnant. This period may last for 60 to 90 days. Here are some common changes you may notice:
Hormonal Changes: High progesterone
Physical Signs:
4. Anestrus Stage
Anestrus is the final stage of your dog’s heat cycle, also known as the resting phase. During this time, her body and hormones return to a baseline state. There are no signs of heat, and she shows no interest in mating. This stage usually lasts 4 to 6 months, though timing can vary based on breed and age. Here’s what you can expect during this phase:
Hormone Changes: Low oestrogen and progesterone levels
Physical Signs:
Hormonal Changes: High progesterone
Physical Signs:
- Vulva returns to normal size
- Discharge stops
- No longer accepts male attention
- May become calmer
- Some dogs show signs of a false pregnancy - nesting, mothering toys, even lactation
4. Anestrus Stage
Anestrus is the final stage of your dog’s heat cycle, also known as the resting phase. During this time, her body and hormones return to a baseline state. There are no signs of heat, and she shows no interest in mating. This stage usually lasts 4 to 6 months, though timing can vary based on breed and age. Here’s what you can expect during this phase:
Hormone Changes: Low oestrogen and progesterone levels
Physical Signs:
- No discharge
- Normal vulva
- No sexual or reproductive behaviours
- Return to baseline personality
- Stable interactions with other dogs
Do Male Dogs Go Through a Heat Cycle?
No, male dogs do not have a heat cycle. Unlike females, they don’t go through hormonal phases, but they can still react strongly when a nearby female is in oestrus (the fertile stage of her heat cycle).
When a male dog senses a female in heat, his behaviour can change dramatically:
- Restlessness, whining, or howling
- Attempts to roam or escape to find her
- Decreased appetite
- Frequent marking with urine
- Aggression toward other male dogs
Can I Stop My Female Dog from Going into Heat?
Some parents may want to delay their dog’s heat cycle due to inconvenience, travel, or other non-medical reasons. However, modifying the heat cycle with hormone-based medications is not recommended for routine use.
These medications can be useful in very specific scenarios, such as controlled breeding or under specialist veterinary guidance. However, they carry significant short- and long-term risks such as:
- Increased chance of pyometra (a potentially fatal uterine infection)
- Higher risk of mammary tumours and endocrine disturbances
- Potential for behavioural changes and complications in future fertility
Can I Spay My Dog While She Is in Heat?
No, spaying a dog when she is in heat is not recommended. Surgical complications, particularly bleeding, are more common if a female is spayed during oestrus, because the uterus is swollen and filled with blood vessels. While it’s possible, most vets prefer to avoid it unless medically urgent.
How Long After a Dog’s Heat Can She Be Spayed?
It's best to wait at least 8 to 12 weeks after your dog’s heat ends before spaying. This allows her hormone levels to stabilise and reduces the risk of complications like excessive bleeding or delayed healing. (Spain et al., 2004; Merck Vet Manual).
The recommended timelines for dogs are:
- Minimum wait: 4–6 weeks to allow the hormones to settle and tissues return to normal
- Ideal wait: 8–12 weeks, especially for large breeds or older dogs
When Should You Spay Your Dog?
The best time to spay your dog depends on her breed and size. Spaying too early or too late can impact her health, so here’s a quick breakdown to help you decide:
- Small Dog Breeds: For small-sized breeds, the ideal time to spay is before or just after their first heat, which is typically around 5 to 7 months of age. This lowers the risk of mammary tumours and supports faster healing. (Oliveira-Martins et al., 2023)
- Medium Dog Breeds: For medium-sized dog breeds, it is better to spay after the first heat or 12 months of age, as it gives enough time for growth while reducing cancer risks. (Hart et al., 2020)
- Large Dog Breeds: Large-sized dog breeds should be spayed after 1-2 heat cycles or between 12-18 months of age. This helps prevent joint problems and urinary issues later in life. (Torres de la Riva et al., 2013)
FAQ
Q: Can I spay my dog while she has her period?
A: Spaying a dog while she is in heat is not recommended. When a female dog is in heat, her uterus is enlarged and has more blood flow, which can increase the risk of bleeding and other complications during surgery. Most vets suggest waiting 8 to 12 weeks after her heat ends for a safer spay.
Q: Is it painful for a female dog to be in heat?
A: The canine heat cycle is not exactly painful, but it can be uncomfortable. Hormonal changes may make a female dog in heat feel restless, clingy, or irritable. Some dogs show no signs of discomfort, while others may act a bit off.
Q: How do you know when your dog’s heat is over?
A: From the first signs of bleeding, most dogs are out of heat in about 3 weeks. However, in some cases, it may last up to 4–6 weeks, depending on biological and hormonal influences.
Q: How long does a dog’s heat cycle last?
A: Most dogs go into heat every 6 to 8 months. The active phase- bleeding and mating behaviour- typically lasts 2–3 weeks. After that, the recovery phase can range from 2 to 8 weeks, depending on the individual dog and her environment.
Q: Is it painful for a female dog to be in heat?
A: The canine heat cycle is not exactly painful, but it can be uncomfortable. Hormonal changes may make a female dog in heat feel restless, clingy, or irritable. Some dogs show no signs of discomfort, while others may act a bit off.
Q: How do you know when your dog’s heat is over?
A: From the first signs of bleeding, most dogs are out of heat in about 3 weeks. However, in some cases, it may last up to 4–6 weeks, depending on biological and hormonal influences.
Q: How long does a dog’s heat cycle last?
A: Most dogs go into heat every 6 to 8 months. The active phase- bleeding and mating behaviour- typically lasts 2–3 weeks. After that, the recovery phase can range from 2 to 8 weeks, depending on the individual dog and her environment.
References
- Spain CV, Scarlett JM, Houpt KA. Long-term risks and benefits of early-age gonadectomy in dogs. J Am Vet Med Assoc. 2004;224(3):380-387.
- Hart BL, Hart LA, Thigpen AP, Willits NH. Neutering of German Shepherd Dogs: associated joint disorders and cancers. Vet Med Sci. 2020;6(1):77–85.
- Kustritz MVR. Determining the optimal age for gonadectomy of dogs and cats. J Am Vet Med Assoc. 2007;231(11):1665–1675.
- Root Kustritz MV. Clinical canine and feline reproduction: evidence-based answers. Wiley-Blackwell; 2010.
- Oliveira-Martins M, Portugal M, Cardoso L, Martins-Bessa A. The Impact of Pediatric Neutering in Dogs and Cats-A Retrospective Study. Animals (Basel). 2023 Aug 1;13(15):2487. doi: 10.3390/ani13152487. PMID: 37570295; PMCID: PMC10417290.
Keywords:
heat cycle of dog,
dog period cycle,
dog in heat ,
female dog in heat
About the author
Dr Rohit Joseph
Veterinary Surgeon, 9 yrs exp
Based in Mumbai, Dr Rohit Joseph is a veterinary surgeon with over eight years of experience. A proud pet parent to senior Indies, Rusky and Tiny, his mission is to elevate pet care in India by empowering pet parents to better understand and nurture their pets
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