Black period blood? We get real about what it means.

Black period blood? We get real about what it means.

Apr 21, 2023Michelle Baker

Black period blood? We shed light on what dark discharge means

Specks, flecks, clots and streaks. Shades of pink, brown, red and everything in between. As we all know, nothing’s off-limits when it comes to periods. But if you’re inspecting your Modibodi undies and notice some black period blood in there, you may feel a little freaked out.

Although it can be alarming, we’re here to let you know that black period blood is usually totally normal. And there are plenty of reasons why it might show up. We’re here to explore the common causes of black discharge and period blood – and what you can do about it.

Why is my period blood black?

We can spot all kinds of unusual things when washing out our period undies, and black blood is no exception. As blood lingers in our bodies, it becomes oxidised through exposure to oxygen. And as it stays there, it turns from red to brown and eventually black.

Usually, you see this black discharge at the beginning or end of menstruation, but it can show up at any time. Try not to worry, though. Black period blood is a natural occurrence because:

  • Periods are all different. The colour of blood can change throughout menstruation.
  • A slower blood flow occurs when the discharge of the uterine lining stops. So it takes longer to come through the vaginal area.
  • Old blood hangs out in your uterus. This could be from previous menstruation that’s just taking a while to come through.

These are all part and parcel of being a person with a period. And in a low volume, black period blood is nothing to worry about. However, if you notice a large amount or you have more symptoms, there are other causes you may want to explore.

Other causes of black period blood

Aside from your uterus taking a little longer to shed its blood and tissue, black period blood can show up for a few reasons. Here are some common causes that might be behind the darker discharge:

  • STIs
  • Endometriosis, PCOS and other conditions
  • Hormones
  • Implantation bleeding
  • Foreign objects
  • Miscarriage
  • Lochia
  • Cervical cancer


Sexually transmitted infections, including chlamydia and gonorrhoea, can lead to rapid degeneration of blood, turning into dark discharge. If you suspect you have an STI, having it checked out immediately is essential, as it can lead to more serious conditions like infertility and pelvic inflammatory disease.

Endometriosis, PCOS and other conditions

Black blood can sometimes be caused by conditions affecting the uterus and ovaries, like endometriosis and PCOS. Black period blood can sometimes resemble coffee grounds and may last up to 7 days in those with endo.


Hormonal changes have a lot to answer for in our bodies. Unsurprisingly, they can also cause black period blood. Thyroid problems, perimenopause (the time before menopause) and excessive uterine stress can cause blood oxidisation and changes in the uterine lining.

Implantation bleeding

A quarter of pregnant people will experience implantation bleeding – when the embryo attaches to the uterine lining. Because it’s just a tiny amount of blood, it can take longer to travel through the vaginal area, causing a black period blood pregnancy symptom that’s pretty tricky to spot.

Foreign objects

Forgotten or stuck objects – like tampons and contraceptive devices – can remain lodged in your vagina, leading to an infection. Sometimes, things like sex toys, condoms and diaphragms can simply irritate the vaginal wall, causing an infection that leads to black blood discharge.


A missed miscarriage occurs when the fetus stops developing but has not physically miscarried. The dark spotting that accompanies a miscarriage usually turns to heavy bleeding as the fetus and tissue pass, but sometimes it requires medical assistance to complete.


Postpartum bleeding and vaginal discharge, known as lochia, can occur up to 8 weeks after giving birth. During the first 5 days, the blood is primarily oxidised, which means it can appear black or dark brown.

Cervical cancer

Unfortunately, it’s not always common to show signs of cervical cancer. However, irregular periods and bleeding after intercourse can be one of them. If you are experiencing troubling symptoms, consult your healthcare professional.

When to reach out to your doctor

We get it. The sight of black period blood and discharge can be upsetting to see. And although a regular thing, it’s worth speaking to your GP if it’s causing you concern.

Black blood showing up with other symptoms, like pelvic pain, pain during and after sex, watery discharge or an unpleasant smell, should be checked out by a health professional. Likewise, if the dark blood appears to be getting heavier or has lasted more than 2 days, let them know.

Hopefully, your GP can help you determine the cause and understand why this black period blood is there.

Staying in touch with your body

A pair of Modibodi period undies makes it easy to stay in touch with your body and spot any changes in your period as they occur. Check out the range of leak-proof underwear and find the best fit for you.

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