When Do Mastiffs Go Into Heat?
Understanding The Signs And What To Expect

When you get a female Mastiff puppy, you often want to know when she will go into heat.  Whether you plan to breed her or not, it will be something on your mind, especially with this being such a large breed dog. A dog’s heat cycle may not be the same as every other dog of the same breed, but there are some general common factors.

When do Mastiffs go into heat?  Female mastiff puppies will go into heat between six months old and two years old. The 18-month gap in the possible onset of the first heat is because of the size of the Mastiff breed. The determining factor in when a dog begins to cycle is her maturity. When she hits puberty and is full-grown, she will have her first cycle.

The average bitch will cycle twice a year for two to four weeks at a time, and extra-large dogs are more likely to only have one cycle a year.  It will take up to two years for your mastiff’s cycle to regulate. While there is no set breeding season for animals, Tibetan mastiffs do tend to have their heat in the spring, differing from other breeds.  Having a dog of this size, there are things to consider while preparing for your dog’s cycle. We’ll get you prepared. Read More Below...

On Sale Now…Our Ultimate Mastiff Care e-book!
Our 90 page e-book has everything you’ll need to know about feeding, socializing, health issues, drooling and shedding control and much more. 57% Off for a very limited time…Check It Out Here.

mastiff in heat


Mastiff First Heat Cycle...What To Expect

If you are new to owning female mastiff dogs, you will want to learn about changes in the dog as they reach maturity and the ability to breed.  Just as there are no two people alike, there are no two dogs alike.  They have their own personalities, likes, and dislikes.  This will become important as your bitch reaches maturity. 

Things to be Aware of When Preparing for Your Mastiff’s Heat

Because this is a big change for your mastiff, it’s important to know more about what she will be going through and how it may affect her – and your family.

Personality Change

Your dogs’ personality can temporarily shift while she is in heat.  She may be protective of your home and family prior to being in heat, and though that will not likely change, she may become more aggressive.

If you have children or other animals, you will want to keep a close eye on them when your mastiff enters her cycle.  If it becomes necessary to keep her away from the other dogs or members of your family, provide her with a space of her own that she can retreat to if she needs time alone. 

She will try to get loose if given a chance, so be aware of this and make sure she is tied out securely when you leave her out to do her business.  Do not leave her unattended.


Pro-tip: Does your Mastiff have issues with anxiety, destructive chewing, aggressiveness, jumping up, barking or fearfulness?

Brain Training For Dogs is an excellent online training course that
addresses these behavioral issues as well as dog training basics.

Physical Contact and Affection

Your dog may no longer want to be pet or patted on the head.  This is not because your dog does not love you or that she has turned mean.  She may simply not want to be social.  This is a stressful time on her body as she prepares for pregnancy and her hormones are elevated making her normal activities less important to her as her only focus is preparing for childbearing.

Your dog may need extra attention.  She may be feeling the equivalent of a person feeling insecure.  She is going through something new; her body is acting differently with her, and she will not know how to react.

Physical Changes

Your dog may be experiencing aches and pains.  We often do not think of this with our pets because they have a high pain tolerance and do not cry when in pain most of the time.  This does not mean your mastiff is not experiencing cramps and body aches.  She may not be as active or agile while in heat.

A larger dog such as a Mastiff will often bleed heavier when in heat.  You may not realize this the first time she cycles or even the second time.  Because it can take up to two years for her cycles to regulate her full flow may not be clear until she is regulated.  Doggie diapers may be something you want to investigate as well as furniture covers for her cycle. 

How Long Does A Mastiff Stay In Heat?

The female Mastiff heat cycle generally lasts from 14 to 28 days depending upon the dogs genetic makeup as well as the dogs age.

This YouTube Video Will Teach More About Your Dogs Heat Cycle...


How To Tell If Your Mastiff Is In Heat

If you know what to look for, you will be alerted that your Mastiff is about to go into heat.  Your dog will have physical signs you can watch for. 

  • Her vulva will become larger.  While this can be missed in smaller dogs, it is rarely unnoticeable in large dogs, such as the Mastiff.  
  • She will also have a bloody vaginal discharge.  This will be darker at the beginning of her cycle and lighten to a pink color as she moves through her cycle. The amount of discharge can vary between dogs, so do not be alarmed if your dog has a heavy discharge. 
  • You will notice your Mastiff will begin urinating more often.  She may also mark her territory by urinating tiny amounts in several spots to release her pheromones to alert male dogs she is ready to mate.  This may also happen indoors.  She is not being disobedient in this case; she is only trying to alert the males in her mating range that she is ready to receive them.
  • She will be eager to allow a male to mount her where she may not have been before her cycle.  She may show signs such as pointing her rear toward the male with a lifted tail lifted to the left side to give him access to her.
  • Her nipples will also get larger sometimes up to four times their natural size.


Pro-tip: Ever try lifting a Mastiff? Their weight can hurt not only your back but their joints when they hop down from cars, sofas or even your bed. To protect your back and theirs check out the best Mastiff ramps on Amazon.com now.



How Can I Help My Mastiff Through Her First Heat

Just as an adolescent human has a challenging time getting used to cycling, this is true of your mastiff as well.  You can explain what is going on to a teenage girl to help ease the symptoms and explain what is going on, but you cannot do the same with your dog. 

She will need different approaches to be guided through her new stage in her life. The same patience and understanding are needed when dealing with your dog, as you would need for a young girl. 

Handling Your Mastiff’s Physical Discomfort

  • Your dog may not be able to tell you what she needs, but you may still be able to help comfort her through this new experience.  With a Mastiff being such a large breed, her cramping and aches may be harder for her due to the extra weight she carries.  If she comes to you for comfort you may want to give her some mild massage on her leg muscles and belly area.  This will help lessen the discomfort of her muscle cramps and aches.

  • Your dog may feel nauseous during her heat, especially during the first one.  There are a lot of hormonal changes going on in her, and this may cause stomach upset.  She may not want to eat her regular food and need a slightly adjusted meal plan.  Chicken is a soft, nutritious alternative that can be given to your dog in combination with or to replace her regular dog food. 

  • Have a place that she can be alone.  Be sure she has her own dog food and water bowl in her space.  If you have other animals, having her separated will prevent any hormonal aggression.  This is a good practice even if she is the only dog in the home so that she has a retreat if she needs space or if she is not feeling well.

Learn more about the topic of Mastiff heat from our page that was written to answer any further questions you might have.


Final Thoughts

Whether you are getting a female mastiff for a pet, protection, or to breed, you will want to prepare for when she goes into heat.  Keep in mind that being well prepared will make the experience easier for you to deal with and less stressful for her, building a stronger bond between the two of you. 


More Helpful Pages From Our Site...


  1. Mastiff Guide Home
  2. Mastiff Dog Information
  3. When Do Mastiffs Go Into Heat