Timings, tags and what to do

  • Unspayed female dogs can have their first heat cycle anywhere between 6 and 15 months of age.
  • During the heat period, which occurs about every six months and lasts a few weeks, your dog can become pregnant.
  • Spaying your dog prevents pregnancy, reduces her risk of cancer, and may extend her life.

If you got your female dog from a pet store or breeder, or adopted her from a shelter or rescue at a very young age, chances are she hasn’t spayed. Then, at some point, your pup will inevitably be in “heat”—the part of his reproductive cycle when he’s open to mating and can get pregnant.

Heat is sometimes referred to as a “canine period” because of the bloody vaginal discharge, but it’s important to note that dogs don’t menstruate in the same way that females do. However, they do have cycles during which they experience a rise and then a decrease in estrogen, and the ovaries release eggs. Heat is a phase of this process when your dog ovulates.

Only male dogs can get pregnant with female dogs who come into heat, says Dr. Megan McCarthy, a veterinarian with Best Friends for Animals. This is why it is essential to pay attention to the signs that your dog is in heat.

Here’s everything to know about dogs in heat — when and how it happens, how long it lasts, and how to tell it’s happening.

How often does that happen?

A small dog with white curly fur sitting on his owner's lap in an open space.

Small dogs tend to have more cycles annually than large dogs.

Emily Hine / Insider



Most dogs will have their first heat cycle between six and 15 months of age. This can vary depending on the dog’s size and breed.

According to Dr. Ole Alcombrack, veterinarian and owner of White Mountain Animal Hospital, dogs typically go into their first heat when they reach about 70%-80% of their maximum weight. McCarthy says that larger breeds tend to start their heat cycles much later than smaller breeds.

Dogs usually go into heat twice a year, or every 6 months or so, says McCarthy, and small dogs tend to go into heat more frequently than large dogs. Smaller strains may cycle three times a year, but very large strains may cycle only once a year.

Heat cycles tend to be pretty consistent, so if your dog has two heat cycles 6 months apart, you can expect that to be the same. However, it can take up to two years for a dog to have regular cycles. Additionally, keep in mind that the length of time between heat cycles can increase as your dog gets older.

What are the signs?

Dog relaxing on couch under blanket.

Your dog may want to cuddle and be closer to you when he’s in heat.

Stephen Cohen / Insider



Identifying signs of your dog’s heat cycle can help you avoid puppies, on the one hand, but it can also help you properly care for your dog.

These signs can indicate that your dog is in heat.

early signs

The first signs of heat appear during “prepartum,” when your dog’s reproductive system is preparing for ovulation. During introductions, male dogs may seem more attracted to your dog, but they will most likely not be receptive to the mating. Even if she mates with a male dog, she cannot get pregnant during this stage.

You may notice the following during the introductions to the liturgy:

  • swelling of the vulva
  • bloody vaginal secretions
  • Hold or tuck her tail close to her body
  • increased clinginess
  • changes in appetite
  • Aggression on male dogs

Alcumbrac says that swelling of the vulva is usually the first symptom, followed by a blood-stained discharge.

Active heat signs

The “estrus” stage is when your dog is in active heat and is able to become fertile. You may notice the following signs during estrus, according to Dr. Amy Attas, veterinarian and founder of City Pets:

  • Less discharge is lighter/pink in colour
  • Less swelling in the vulva
  • More acceptance and friendliness towards male dogs
  • Increased vocalization, especially whining, wailing, and crying
  • More aggressive towards female dogs
  • Restless or nervous behaviour
  • urinating more than usual
  • Increase the attractiveness and interest of male dogs
  • “Flag” – raising her bottom towards male dogs or moving her tail to the side

It’s not uncommon for female dogs to urinate in small amounts on various things in the house or outside while in heat, says Attas. This is because during estrus, their urine contains pheromones and hormones that signal their reproductive status to male dogs.

How long does the heat last?

The dog lies on his back with a warm toy between his paws

Dog cycles usually last the same length of time for each cycle.

Elena Matarazzo / Insider



The heat cycle lasts about 18-21 days.

According to Alcumbrac, proestrus averages about 2-11 days, and estrus usually lasts 3-5 days but can be as long as 11 days.

The length can vary based on your dog’s breed, size, and age, but once your dog starts having regular cycles, you can expect your dog to stay in heat for about the same amount of time.

What should I do?

Knowledgeable employee Danny Backst walking his dog.

Take your dog for more frequent walks when he’s in heat because he may need to urinate more often.

Danny Baxt/The Insider



Your dog may need a little TLC while in heat. Fluctuating hormone levels can have a significant impact on her both physically and behaviorally, which is why McCarthy advises giving her plenty of attention and rest.

To care for your dog during heat, you can:

  • Take her on frequent short walks. She may need to urinate a lot while she’s in heat, and light exercise can also help release her pent-up nervous energy or aggression. Consider taking walks earlier in the morning or later in the evening, when there is less dog traffic in your area. Never force your dog to walk if she seems tired – instead, let her rest.
  • Provide him with chewable toys to distract him and help relieve stress.
  • Avoid reprimanding or exposing the dog for any messes due to a bloody discharge. Speak in a gentle, reassuring voice.
  • Make sure your dog drinks plenty of water and eats well.
  • If you have multiple dogs, make sure they have their own food bowl, water bowl, and bed to avoid squabbling.
  • Make time to pet her, massage her, and brush her coat, all of which can be soothing and calming.
  • Give her plenty of space and allow her to start cuddling and interacting.

If you use dog diapers, McCarthy says it’s important to change them often — at least every three to four hours — to prevent skin irritation and urinary tract infections.

Keeping your pup away from unneutered male dogs is crucial if you’re trying to prevent pregnancy, says Attas. McCarthy suggests avoiding dog parks, group training events, and other events involving other dogs while you’re in heat.

Never leave your dog alone outside, and always keep him on a leash when you go for walks. You may also want to keep windows closed to prevent male canine visitors from showing up in your home.

When do you get your dog sterilized?

McCarthy says spaying your dog as soon as possible is the best way to prevent your dog from becoming pregnant, especially if he spends a lot of time with other dogs.

The American Animal Hospital Association recommends spaying before your dog’s first heat session:

  • Five to six months of age for breeds under 45 pounds when fully grown
  • 5-15 months for breeds over 45 pounds when fully grown

“We usually want to allow large breeds to grow more before spaying because this procedure can change the way their bones develop,” says Alcumbrac.

If you are not sure when is the right time to spay your dog, consult your veterinarian.

The benefits of sterilization

Each year, approximately 3.1 million dogs enter US animal shelters. Due to overcrowding, approximately 390,000 people were killed. Therefore, unless you have a specific plan for small dogs, spaying your dog is the best way to prevent further unnecessary early dog ​​deaths.

Experts also say that neutering can have multiple health benefits for your dog. In fact, a 2013 study found that the life expectancy of spayed dogs was 26.3% longer than that of non-spayed dogs.

One reason is that neutering reduces your dog’s risk of developing mammary cancer and pyometra (a fatal uterine infection that occurs as a result of hormonal changes in the reproductive system).

Breast cancer is the most common type of tumor in untreated female dogs. In fact, nearly half of mammary gland tumors in dogs are cancerous.

But spaying your dog reduces the production of hormones that can contribute to the growth of these mammary gland tumors. This is why dogs that are spayed before they first heat have only a 0.5% risk of developing breast cancer.

This risk increases to 8% if they are spayed between the first and second heat cycles and jumps to 25% if they are spayed at any time after the second heat.

Finally, neutering your dog can reduce some behavioral problems, including:

  • aggression
  • Roaming
  • Excessive pronunciation
  • urine signs

An informed takeaway

All un-spayed female dogs go into heat—the stage in their reproductive cycle when they are open to mating and are able to become pregnant. If you can recognize the early signs, you have a better chance of preventing your dog’s pregnancy.

When you notice signs of heat, you can reduce the chances of an unwanted pregnancy by always using a leash when you take them outdoors and keeping them away from dog parks or other areas that may have unneutered dogs.

In addition to protecting your dog from pregnancy, you’ll also want to make it a point to provide her with plenty of comfort.

Remember: while spaying is a personal decision that only you as the owner can make, it can also offer a host of benefits to you and your beloved puppy.

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