Why Are My Dog’s Nipples Enlarged After Heat?

Why Are My Dog’s Nipples Enlarged After Heat

When dogs go into heat you will be witness to a lot of changes. You will see subtle, and not so subtle differences occurring. These can include changes in their behavior to aspects of their physical appearance, for example, the size of their nipples (mammary glands).

What catches many pet owners by surprise is how swollen the mammary glands will be after heat. Several days later in fact, it will appear that your dog’s nipples are still enlarged. But why is your dog still swollen after heat? Here’s the lowdown…

Why are my dogs’ nipples enlarged after heat? Your dog’s nipples are enlarged after heat due to the high level of progesterone hormone remaining in their body. This high hormone level is responsible for swollen mammary glands after first heat.

Another possibility for your dog’s nipples being enlarged after heat could be pregnancy. Some dogs will even experience a false pregnancy which can result in real physical symptoms like swollen mammary glands.

Below contains a quick guide on this phenomenon, how you can help your dog if it’s painful, and how long do dogs nipples stay enlarged after heat

Dogs has swollen mammary glands after first heat

If you own a female dog, you will surely agree that when she’s in heat, you see a hugely different side to her. And if there’s one thing you can’t fail to notice, it’s the enlarged nipples days or even weeks after their peak heat period.

This can be a little disconcerting, as swollen mammary glands in a dog can be a sign of pregnancy. It’s no wonder that so many dog owners start to worry!

But before I proceed with the details of why this your dog has swollen mammary glands after heat and how long it can last please note – it’s perfectly normal to see your dog with swollen nipples many days after the heat phase.

If you’re treating your gorgeous canine friend to a belly rub session and you spot big nipples post-heat, by all means, carry on with the rub — no need to panic and phone your vet.

The only time you should worry and reach out to your vet is if there’s more going on apart from the swelling (I’ll get back to this with details)

Before we take a closer look at why dog’s nipples get bigger after the first heat, let me share the basics of why your dog’s nipples change in size when they’re on heat.

Why your dog is still swollen after heat

When your dog goes into heat, her body is basically getting ready for pregnancy. As a result, the level of hormones in her body will shoot up more than usual.

I’m referring to the estrogen, progesterone, and luteinizing hormone levels.

These are the three main hormones present in your dog’s body during the actual heat phase (estrus stage). Because these hormones are abnormally high, they’ll trigger more blood supply to your dog’s mammary glands.

The sudden blood flow to your dog’s teats will make the nipples feel firmer, become enlarged, and look bigger. Plus, the pinkish color will be popping!

It all happens because of natural hormonal influences.

The post-heat stage in dogs is known as the diestrus period. That’s when your dog’s interest in sexual activity drops completely, so in essence, they aren’t in heat.

Even though your dog doesn’t have the will to mate, their nipples during this stage will still look as large as they did during the estrus stage.

There are three main explanations behind this.

1. Their progesterone level is high

As I mentioned a few moments ago, a dog in the diestrus phase has no urge to mate. At all. That’s because the level of estrogen and luteinizing hormones in their body during this phase is quite low.

Estrogen is what gives your canine friend strong sexual urges. Luteinizing hormone, on the other hand, is known to stimulate estrogen levels.

Although these two hormones are almost out of the picture during the diestrus phase, progesterone levels will still be high. Extremely high, for that matter.

One of the many functions of progesterone in a female dog’s body is to trigger changes in the dog’s mammary glands tissues. So, if there’s lots of this hormone in your dog’s body after heat, it makes sense why they’d have enlarged and swollen nipples. The progesterone is still at work.

How long do dogs nipples stay enlarged after heat? In most cases, a dog’s nipples will stay enlarged for up to 4 to 6 weeks after heat, before they return to normal size.

2. Your dog is pregnant

Another reason your canine friend’s nipples might be bigger after heat is they probably got pregnant during the estrus phase.

If you weren’t keen on keeping an eye on your female pooch when their sexual urges were at the peak, chances are, they messed around.

What I’m trying to say is if you allowed your dog to roam the neighborhood unleashed when they were in heat, and the size of their nipples hasn’t gone down 6 weeks after the heat phase, it’s likely they’re pregnant.

When your dog is pregnant, the progesterone levels will drop, and another type of hormone takes over the body —prolactin hormone.

Prolactin influences milk flow to a pregnant dog’s teats as their body prepares for lactation.

So, when milk flow to your canine friend’s teats increases, so will the size of their nipples.

Handy Hint: Dogs will also get period cramps during this time, just like human females can. They can be a little painful, but you can help relieve them for your dog.

3. False pregnancy alert

Yup! False pregnancies in dogs exist. Many dogs experience this after heat.

And there’s a medical term for it — pseudocyesis or pseudopregnancy.

Even though your dog didn’t get pregnant, there’s a possibility of them experiencing a false pregnancy. This is when a dog isn’t pregnant, but their body acts like it and shows all the signs – here’s what VCA Animal Hospital says:

“Signs of false pregnancy usually begin four to nine weeks after the previous heat period and mimic the signs of true pregnancy. The more common signs of pseudo-pregnancy include mammary gland enlargement with or without the production of milk, lethargy, periodic vomiting, and fluid retention.”

It happens because of the hormonal changes that dogs deal with post-heat.

Your dog’s body was already preparing to get pregnant during the heat period, but your dog behaved herself (with your help, of course). So, no pregnancy.

But even then, their body might still release the prolactin hormone after heat. This hormone will trick your canine friend’s body into performing functions that a pregnant dog’s body would — one of them, stimulating milk flow to the teats.

That means false pregnancy can leave your dog’s mammary glands becoming swollen and the nipples bigger.

You’ll know your dog is going through a pseudo pregnancy if you are 100% sure you didn’t leave them outdoors alone during the heat period, but they’re still displaying all the signs of pregnancy.

Typically, the false pregnancy phase (including all its signs like enlarged nipples after heat) goes away in 2 to 3 weeks.

As you can see, you have nothing to worry about if your dog’s nipples aren’t back to normal size immediately after the heat phase. Provided they aren’t pregnant, they’ll be fine in a few weeks.

Here’s when you should worry about enlarged nipples

You have all reasons to freak out and visit your vet if you observe the following:

  • The nipple color is different from the usual pinkish or darkish color.
  • There are constantly scratching or excessively licking their nipples (dogs have between 6 and 12).
  • The nipples’ swelling has gone beyond six weeks, yet you are sure you closely monitored your furry friend throughout their heat period (so they aren’t pregnant).
  • There’s pus or blood coming from the nipples.
  • There’s the presence of lumps on the nipples area.

These symptoms might indicate your dog has an infection, an allergic reaction, or a serious underlying medical problem. Only your vet can know which is which, that’s why seeking professional help is necessary.

Handy Hint: Here’s a list of 9 common behaviors you will witness once your dog is in heat.

Related questions

Do female dogs’ nipples go back to normal after heat?

Yes, that is correct. If a dog doesn’t get pregnant during the heat phase, their nipples will return to their usual size around 4 to 6 weeks after heat.

Can a dog’s nipples swell if not pregnant?

Yes, that’s right. During and after heat, a dog’s nipples will still swell because of the non-pregnancy-related hormones in their body.

What does it mean when a female dog’s nipples are swollen?

It simply means there’s a lot of blood flow or milk flow to the dog’s teats (during and after heat), which makes the nipples look larger than usual.


Dogs’ nipples can get bigger after the first heat, but should retract back to their normal size within a few weeks.

Given most dogs will only go into heat 2 or 3 times a year, it’s something that you will only notice now and again, and it nothing to be worried about if it’s related to her being in season.

You might also like…

Image in header via https://pixabay.com/photos/golden-retriever-dog-grass-smile-1809044/

Marc Aaron

I write about the things we've learned about owning dogs, the adventures we have, and any advice and tips we've picked up along the way.

Recent Posts