Do Guinea Pigs Menstruate?

Do Guinea Pigs Menstruate

When it comes to the menstruation, some animals are very similar to humans. The finest example of that is female dogs. When you see some blood coming from their genitals, that means that the estrous cycle is happening.

But, do guinea pigs menstruate? The answer to that question is simple – no. Guinea pigs do have an estrous cycle, but it’s displayed quite differently compared to other mammals. Some guinea pig owners reported that they’ve seen their guinea pigs bleeding from behind, but this bleeding can come from the anus, and not necessarily from a vagina. In either of these cases, it doesn’t mean that your guinea pig is menstruating.

If guinea pigs don’t menstruate, how is it possible that there’s blood coming from behind? We’ll talk more about that in this article.

Possible Causes of Bleeding

Bleeding from the genitals in some animals is not a cause for concern. However, guinea pigs don’t bleed from their genitals and if you see that this happens, it’s definitely a reason to visit the vet as soon as possible. Wondering why this bleeding can happen? Here are possible reasons:

  • Urinary Tract Infection

The most common reason for bleeding is urinary tract infection. It’s not strange that many guinea pig owners think that their pig is menstruating. On top of that, bleeding from the genitals, in this case, is subtle, yet can be quite noticeable if you take a good look. The infection of the urinary tract usually include bladder inflammation (cystitis) and this condition can cause the blood to get into the urine. Simply put, blood from bladder inflammation in conjunction with urine makes a guinea pig bleed.

Sometimes the blood appears when your guinea pig tries to urinate but sometimes, the blood just drips from the genitals, even if the pig isn’t trying to urinate. That’s why we said that it can be quite noticeable. If you want to make sure that this blood is benign, you’ll need to either take your guinea pig to the vet or try to collect the urine directly from the guinea pig. This is a tricky part, though, as guinea pigs mostly urinate at the same place, probably in the litter box.

The test of your guinea pig’s urine is pretty simple and will show if your guinea pig has a urinary tract infection or any kind of infection that causes bleeding. That’s why it’s very important to notice these symptoms on time thus making sure that it’s treated well.

  • Tumors

Another less common reason for bleeding is the existence of tumor in the body or urinary tract. A cancerous growth, whether malicious or benign, can be very dangerous and almost always cause bleeding. The bleeding from this type of tumor is almost the same as with urinary tract infection and can easily be mistaken for menstruation. Since the tumor is probably located somewhere inside the urinary tract, the blood that comes out has a dark red color. Remember that darker blood always comes from the inside and lighter blood comes close to the outside of the body.

The blood from the tumor comes exactly from the tumor itself. The existing tumor can be removed with the surgical process and it’s up to the vet to decide whether or not to remove it. Benign tumors can be removed, but sometimes, the symptoms can be kept to a minimum with medication. Malicious tumors are much more dangerous and require immediate surgery. The only real way to find out if there’s a tumor is to take your guinea pig to the vet to do MRI, ultrasound, and other necessary analysis.

  • Pyometra

Pyometra is an excessive amount of pus in the uterus. It doesn’t come from the urinary tract, but exactly from the uterus and it can be quite problematic. In fact, almost every mammal can suffer from this condition, with dogs and cats being the most common example, as domestic animals. The pus in the uterus is a byproduct of a serious infection that can rarely be cured with antibiotics.

Instead, the best solution is an emergency surgery which often involves spaying of a guinea pig. Actually, the best outcome will be if you spay your guinea pig. Spayed guinea pigs don’t have any potential risks of developing pyometra.

  • Uroliths

Remember the article where we talked about salt and potential risks of bladder stones? Well, these exact same stones develop a condition which is called uroliths and it’s a pretty common condition that guinea pigs can develop. Uroliths is caused by an excessive amount of minerals, which then turn into microscopic crystals. These microscopic crystals form and develop a stone, which then makes your guinea pig bleed.

The bleeding occurs directly from the urinary tract, and in this case, the guinea pig will have a hard time urinating. The tiny mineral particles go through the urinary tract and scratch the walls, making the process of urinating painful and cause bleeding. There’s nothing to worry about if you visit the vet as soon as possible. However, surgery is the only option here. Your veterinarian will remove the stones that are too large to pass through the urinary tract.

This condition can be prevented by reducing calcium in your guinea pig’s diet, as well as buying fresh water.

  • Bleeding in Estrous Cycles

Is bleeding possible in estrous cycles of a female guinea pig? As a product of estrous cycle – no. A medical condition in conjunction with an estrous cycle is something that can produce bleeding, but again, the estrous cycle doesn’t have anything to do with the bleeding. As guinea pigs go through the multiple estrous cycles throughout the year, it’s important to know something about that, too. Every heat cycle lasts anywhere from 14 to 19 days. There are also periods of 12 to 15 hours in which the sow is receptive to the boar.

The estrous cycle can still occur, even when the guinea pig is pregnant. Sometimes can happen that the guinea pig can be pregnant while nursing the existing litter.

So, how can you notice an estrous cycle in your female guinea pig? The tricky thing is that guinea pigs often don’t display any kind of symptoms. Some female guinea pigs will try to mount on other female pigs, which can sometimes be a symptom. Male guinea pigs will, on the other hand, easily notice when a female is in heat period. The male pigs will then chase female pigs often and try to mount on them.

That being said, you aren’t going to notice a heat cycle by yourself but if you have male guinea pigs, it’ll make things easier.

Is Spaying a Guinea Pig Going to Prevent Bleeding?

As we mentioned earlier, if your guinea pig gets the infection of the uterus, the great solution is to spay it. But, can spaying reduce the risks of potential bleeding? In some cases, yes. Every kind of bleeding that comes from uterus can be prevented by spaying. The bleeding that comes from urinary tract can’t be prevented in that way. The best way of preventing bleeding is to give your guinea pig fresh water with no minerals in it. Fibers are also a great way to improve overall digestive processes and since high-fiber food has a lot of water in itself, it’s also great for the urinary tract.

Preventing development of tumor in the reproductive tract of your guinea pig is also possible. Of course, spaying is a great option and you should do it after 4-6 months of age. Remember that guinea pigs don’t need to mate and they can live perfectly fine without it. So, if you plan on keeping only one guinea pig, you should definitely spy it, whether it’s male or female.


Guinea pigs can’t menstruate but can display symptoms that can be mistaken for menstruation, especially for inexperienced guinea pig owners. A guinea pig can’t menstruate and bleeding shouldn’t occur even when in heat cycle (female guinea pigs). Instead, the heat cycle has different symptoms that aren’t similar to any symptoms we’ve mentioned before.

If you see your guinea pig bleeding from either anus or genitals, you should immediately visit the vet. By determining the cause of bleeding on time, you can save your guinea pig’s life and make the process of curing the disease much easier.

Furthermore, spaying your guinea pig is going to reduce chances of any kind of bleeding from genitals.