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If your female dog is not spayed, she will go into heat roughly twice per year.

Matilda had her last heat in late May, and didn’t have another until mid-January. So, her heat cycle is about 7.5 months long.

Your dog’s first heat cycle will occur when she’s between 6 months to 2 years old.

Matilda and Cow had their first cycles when they were 9 months old. Human women are said to sync up their periods if they spend a lot of time together, so perhaps this can happen to dogs, too.

The Estrus Cycle

When your dog is in heat, she will bleed from her vulva. This is not the same as a human woman’s monthly menstrual cycle.

A dog’s heat cycle has four stages:

  1. Proestrus (average, 9 days) Your dog’s vulva will be swollen, and she will have bloody discharge. She’s not interested in mating with males, though her milkshakes will bring all the boys to the yard. Random males may appear on your property or follow you during walks. A male can smell a female in heat for up to 3 miles. Your female will tuck her tail to protect her vulva.
  2. Estrus (average, 9 days) Your dog’s vulva will still be swollen, and her discharge will lighten to a pinkish or pale yellowish color. Now, she’s receptive to males and will present her rump to them, and shift her tail to the side so they can access her vulva.
  3. Diestrus (60 days) Your dog is no longer receptive to mating, and males are no longer interested in her. Her vulva shrinks and progesterone declines. If she is impregnated during her heat cycle, this will be her pregnancy.
  4. Anestrus (4+ months, until next proestrus) your dog is her usual self, and slowly preparing for her next cycle.

 Do Dogs Get “Period” Cramps?

I have not found substantial evidence whether or not dogs suffer from uterine cramps when they are in heat.

I wouldn’t be surprised if they did suffer from mild cramps. A human woman experiences painful uterine contractions to help expel uterine lining when she is on her period. So, a dog’s uterus may also contract to help expel blood.

Bananas, with their high potassium content, are said to help ease cramps in humans, so they might do the same for dogs. Give your dog a small amount, just a few bites – not enough to replace a whole meal.

You may also want to try CBD oil to reduce pain and inflammation. CBD oil can also take the edge off any anxiety or behavioral changes that your dog might be experiencing around this time.

I like keeping CBD oil around the house. It’s good for moments when you think your dog might be experiencing mild pain or discomfort, without any risk of side effects or the risk of over-medicating.

Should We Still Go On Walks?

Dogs in heat can still go on walks and enjoy their usual activities if they seem up to it.

If you go for a walk in a neighborhood where loose male dogs are around, you’ll likely get followed along the way. This could become a problem if your bitch or the male dog becomes aggressive, or tries to mate.

As always, keep your dog on a leash.

You may want to carry a spray bottle, taser (for the noise, only taze a loose dog if they’re a serious threat) or other deterrent to keep male dogs away. I’d never recommend these items for use on your own dog, but when it comes to protecting your own from others, you do what you have to do.

I often daydream about protecting my dogs from any threat, and would gladly fight a dog that weighs more than me to get Matilda loose from its jaws. Bring it on, dog!

Male dogs can be very persistent. While they may usually run off if you tell them to go away, the temptation of your dog’s heat may give them way too much courage.

Needless to say, no dog parks or play dates.

Other bitches and neutered males might have strange reactions to your dog’s heat.

When Matilda and Cow were in heat at the same time, Cow mounted Matilda (yes, you read that correctly,) putting her at risk for serious injury.

Later, when Cow was spayed and Matilda was in heat, she tried to mount her again. Never did Matilda reciprocate. Matilda’s tail curled to the side as though she was receptive to Cow’s lady babies. It was very, very weird.

What To Wear


You can find an array of disposable and reusable panties at your local pet store. You can also improve with socks, homemade underwear, or you can just lay towels where your dog lays.

No type of panties will stop a male dog from penetrating your dog. There are “chastity belt” devices sold under the premise of being able to stop a determined dog, but I would be careful about using them without supervision, as they won’t keep either dog safe if the mating attempts escalate to aggression.

You may find that your dog dislikes wearing panties. Like Matilda, she may squirm out of any pair. She may lick herself often enough to keep most drips from staining your furniture.

Give your bitch a few hours of free time each day to take care of herself. Lay down a towel or give her time for self-care in her crate.

How To Make Your Chihuahua Sock Panties

How to make heat panties out of a sock to catch estrus drips from a small dog.A clean, stretched sock can make absorbent underwear for a small dog.

Cut long slits up the sides for leg holes. The leg slits should be long, not wide, leaving a wide crotch area for full coverage.

Then, put the underwear on your dog and mark a hole for her tail, then cut a hole or a X for her tail to poke through.

Make several pairs of sock panties, changing daily to wash clean.

For a larger dog, you can sew a diaper or fashion something from a child’s garment. You can insert an unscented pantyliner to keep her fresh and clean.

No matter what you use to contain your dog’s drippings, make sure it’s clean. Change at least once per day, and give your dog some free time to clean themselves as nature intended.

Unsanitary conditions may lead to the uterus infection pyometra.

Beware Of Pyometra

Two to eight weeks following your dog’s heat, they are vulnerable to uterus infection, known as pyometra. 

When your dog is in heat, their body is preparing them to become pregnant. White blood cells that normally protect the uterus from infection are not present to allow sperm to enter and survive.

Progesterone causes thickening of the uterine lining. The cervix is open to allow sperm to enter. If your dog does not get pregnant, their uterus is now vulnerable to infection.

When the cervix is open, it’s called an open pyometra infection. Pus may leak from your dog’s vulva. A closed cervix means pus is not able to drain, in the case of a closed pyometra infection. This is even more life-threatening and can cause your dog’s belly to distend.

Fever, restlessness, vomiting and diarrhea are all signs that your dog may have life-threatening pyometra.

Watch your dog closely after her heat cycle. Take her to the vet immediately if you suspect she has an infection. If it’s after-hours, an emergency vet visit is in order.

The best way to treat pyometra is for your vet to spay your dog, removing the infected uterus. Left untreated, your dog will most likely die.

When Should You Spay Your Dog?

Your dog can be spayed as young as 6 weeks of age, and at any time after that.

Spaying your dog while they’re in heat is risky. The uterus is engorged and may bleed more. In Cow’s old life, I didn’t fully take on ownership of her until after she had her babies. I had her spayed during her first heat after the pups.

The vet said the fact that her uterus was permanently stretched from having pups, and her being in heat were both risk factors. Even so, she recovered quickly without any complications.

Matilda is 2.5 years old, and on her fourth heat cycle. I’m afraid to get her spayed because so many dogs in my chihuahua Facebook groups die from surgery complications.

My vet assured me that they would do bloodwork to check for any risky underlying conditions, but I still worry. I don’t have any plans to get her spayed at this time.

UPDATE: Matilda was spayed at three years old. There were no complications. Veterinarians spay tiny kittens at just a few weeks old, so I no longer feel it’s such a dramatic risk for an adult Chihuahua, even a tiny one, to go in for a routine spay.

In some parts of the world, people only spay their dogs if there’s a medical reason. They are said to have fewer overpopulation problems because dog owners are responsible with their dogs, preventing pregnancy when they’re in estrus.

Spaying your dog eliminates the possibility of pregnancy and pyometra, as well as certain cancers.

Not spaying your dog allows them to have all of their hormones in-tact as they mature.

To spay or not to spay? It’s a personal decision. Do your research and choose wisely.

The four stages of your dog's heat cycle: proestrus, estrus, diestrus and anestrus.

Lindsay Pevny
Lindsay Pevny lives to help pet parents make the very best choices for their pets by providing actionable, science-based training and care tips and insightful pet product reviews.

She also uses her pet copywriting business to make sure the best pet products and services get found online through catchy copy and fun, informative blog posts. She also provides product description writing services for ecommerce companies.

As a dog mom to Matilda and Cow, she spends most of her days taking long walks and practicing new tricks, and most nights trying to make the best of a very modest portion of her bed.

You'll also find her baking bread and making homemade pizza, laughing, painting and shopping.