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When Do Lab Puppies Go Into Heat?

Two cute Labrador puppies Laying down and looking ahead

Being a large dog breed, Labrador puppies usually go into heat a few months later than most other dog types. On average, a female Lab will go into heat for the first time when she’s around 9–12 months old.

There are a few rare occasions when they can start at about six months of age. Then, there are those late bloomers who experience their first heat much later, when they’re nearly 18 or even 24 months old.

As long as your Lab is healthy and strong, there should be nothing to worry about.

Read ahead to learn more about a Labrador’s heat cycle.

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All About a Dog’s Heat Cycle

A heat cycle refers to the time a female dog becomes fertile and can get pregnant. Like humans, this is typically when they reach puberty.

Yet, for dogs, it can be as early as four months or as late as 24 months, depending on the breed.

The heat cycle is divided into four stages, which your female Labrador will go through once or twice a year.

During these stages, her body produces the hormones needed to maintain her fertility throughout the year.

Proestrus

  • This is the 1st stage of the heat cycle when estrogen levels reach their peak
  • It can last up to nine days
  • The uterus gets ready for a potential pregnancy
  • Vulva becomes swollen
  • Bloody discharge starts to appear

Estrus

  • The 2nd stage of the cycle is when female Labs can get pregnant
  • Referred to as ‘in season’ or ‘going into heat.’
  • It lasts nearly nine days.
  • The vulva is still a bit swollen but starts to soften up a bit
  • There’s fewer bloody discharge that becomes a lighter shade of pink
  • Estrogen levels drop, while progesterone levels begin to rise

Diestrus

  • The 3rd stage of the heat cycle
  • Female Labs stop being responsive to males during this stage
  • This stage can last between 2–3 months, or until she gives birth if she’s pregnant
  • If there’s no pregnancy, your Lab’s body takes this time to go into a period of rest and recovery
  • Both estrogen and progesterone levels return to normal during this stage.

Anestrus

  • The 4th and final stage of the heat cycle before the next proestrus, or heat, occurs.
  • Typically lasts four months but can be longer for some breeds
  • During this stage, your Lab will no longer be in heat, nor will she be fertile
  • She also won’t show any interest in male dogs, nor will they be attracted to her
  • No discharge of any kind
  • The vulva returns to its normal size and color

How Long Do Labs Go Into Heat?

Yellow labrador retriever

For the average female Labrador Retrievers, the heat cycle can last anywhere between two to four weeks.

During the first few days of the cycle, or the proestrus stage, female Labs won’t show much interest in male suitors.

Then, when they start the second stage, they become more welcoming and reciprocate their advances.

Some, however, are receptive to the males from the beginning of the cycle until the end. So, keep an eye on your Lab to determine what her typical behavior will be.

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How Often Do Labs Go Into Heat?

Once the heat cycle ends, which is typically after 18 days, the female’s fertile period is over. This means that if she wants to get pregnant, she has to wait several months for the next heat cycle to begin.

Unlike human females who go through a monthly menstrual cycle, female Labrador Retrievers will go into heat around once every six months.

Your vet will probably recommend that you mark down when her first cycle begins. Then, count six months after that date.

Bear in mind, however, that not all female dogs are the same. This time frame may vary from one Labrador to the next.

In other words, it’s not unusual for some female Labs to go into heat every 3–4 months. On the other hand, others may be in season only once a year!

As long as the cycle is regular and follows a consistent pattern, there’s no need for concern. However, if you notice any irregularities in your Lab’s cycle, consult with your vet.

Late or irregular heat cycles can be an indication of various health conditions that require immediate medical attention. They could also result from malnutrition, excessive physical exercise, or medicines that cause a hormonal imbalance and affect fertility.

Signs Your Dog Is Going into Heat

Labrador jumping up with onwer

Most female dogs will start to experience their first heat at around six months. However, smaller breeds sometimes can begin as young as four months old.

On the other hand, larger breeds, such as the Labrador Retriever, tend to be older, even as old as two years old sometimes, before they have their first heat cycle.

There are usually distinct signs that tell you when your Lab is in heat.

Yet, there are rare cases when the female goes through what’s called a ‘silent heat cycle.’ This is when she goes into heat but doesn’t show the usual symptoms we’ve listed below.

In cases like this, your vet can check your Lab for a silent heat cycle. First, the vet will need to perform vaginal cytology. This is where they take a swab of the vaginal wall cells with a cotton swab.

The vet will likely also take a blood sample to measure progesterone levels in your female Lab’s blood.

For most other dogs, the signs are clear as day. Here are four signs to help you determine when your dog is going into heat:

  • The vulva becomes redder and increases in size, sometimes up to 2–3 its usual size
  • Red vaginal bleeding, which you may not even notice unless you’re paying close attention
  • When the female is in peak heat, or the most fertile stage of estrus, the bleeding usually stops
  • Increased self-cleaning and licking of the vaginal area
  • Your Lab may be restless and easily excitable at times, or she may be more aggressive or skittish than usual
  • In full heat, the female will curl her tail to one side, which is known as ‘flagging’