Home About Labradors Facts About Labrador Heat Cycle You Must Know

Facts About Labrador Heat Cycle You Must Know


Do you own a female Labrador? Whether you plan to breed your Lab or not, you must understand how Labrador heat cycle works to avoid ending up with an unplanned litter of puppies or failed breeding attempts.

What does the phrase ‘dog goes into heat’ mean?

When a dog goes into heat, it means she is in the stage wherein her body is getting ready for possible conception. To better understand this, you must know that a dog’s heat cycle is divided into four stages – proestrus, estrus, diestrus, and anestrus.

Your Labrador dog goes into heat during the first three stages, which are also called “active heat.” During these stages, your Labrador’s body is getting ready for possible pregnancy. Dogs are most fertile 9 to 13 days after her “active heat” starts. The fertile period typically lasts for 5 days.


When do Labradors start going into heat?

A female Labrador’s body matures and prepares itself for reproduction as she grows. Generally, a dog’s heat cycle begins when she is between 6 and 12 months. Large dogs may experience their first heat when they turn 10 months old. On an average, Labrador Retrievers start going into heat when about 9 months old.


What happens during each stage of Labrador heat cycle?


Your Labrador’s body isn’t fertile yet during this stage, but her body is preparing itself for possible pregnancy and puppy birth. During this stage, the pituitary gland secretes hormones that stimulate the growth and development of follicles, which are fluid-filled sacs that contain immature eggs. The follicles are located within the ovaries.

During this stage, your Labrador shows physical signs of heat. However, she won’t be receptive to a male dog’s attempts to mate with her. Your Labrador’s vulva starts to swell gradually with pinkish to reddish discharge. The stage typically lasts for 9 to 10 days.


During the estrus stage, the estrogen level in your Labrador declines while her progesterone level goes up. The ovary releases eggs at the beginning of this stage. This is the stage when your dog becomes fertile. She then starts to be amenable to a male dog’s attempts to mate with her.


It is the final part of your Labrador’s “active heat” and lasts for 4 to 8 weeks – sometimes even longer. During this stage, the progesterone – the hormone that maintains pregnancy— remains high. Your Labrador looks disinterested interested in a male dog’s attempts to mate with her. Male dogs also lose interest in your female. Bloody discharge may still be present during the diestrus stage. It stops gradually. The vulva also returns to its normal size during this stage.

If your Labrador gets pregnant during the estrus stage, the diestrus stage continues until she gives birth to the pups, which usually takes 60 to 67 days following the conception.


This is the final stage of a dog’s heat cycle. The anestrus is the “resting” stage, and there is little to no ovarian activity during this time – until your Labrador’s “active heat” starts again. This stage lasts between 130 to 150 days.

With no ovarian activity, your Labrador’s body returns to normalcy. Your Labrador’s reproductive system also takes rest and prepares for the next possible pregnancy.


What signs will you see when your Labrador dog goes into heat?

Hormonal changes cause your Labrador’s body and behavior to undergo changes. Listed below are some signs indicating that your Labrador is going into to heat.

  • Swollen breasts
  • Enlarged vulva
  • Increased thirst
  • Increased urination
  • Bloody discharge
  • Tail-flagging
  • Clinginess
  • Being more affectionate than usual
  • Male dogs following her everywhere
  • Male dogs fighting over your Labrador


How often do Labradors go into heat?

The frequency of heat cycle varies per dog. Depending on the dog, it may occur at least once in 6 to 8 months. Most dogs go into heat twice a year.


When do Labradors stop going into heat?

A dog’s ovarian activity begins to decline in the 6th year of her life. Most dogs stop conceiving from 7th year onward.