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

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

Feb 07, 2024Michelle Baker

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 find yourself rinsing your period pants and notice some black period blood, 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. So, let’s explore the common causes of black discharge and black 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 pants, and black blood or discharge 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. This is why you might see black period blood at the beginning of your period.


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 and is easily managed with a pair of period pants. However, if you notice a large amount or have other symptoms, it’s best to visit your GP to make sure it isn’t anything more serious, as there are a number of other things that could be causing it.

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 or black discharge:

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



Sexually transmitted infections, including chlamydia and gonorrhoea, can lead to rapid degeneration of blood, turning into dark, almost black discharge. If you suspect you have an STI, getting 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 or seems out of the ordinary.

If you’re asking yourself ‘why is my period blood black’, and you’re experiencing other symptoms like pelvic pain, pain during and after sex, watery discharge or an unpleasant smell, it 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, it’s best to consult a doctor.

Hopefully, your GP can help you determine the cause and a treatment if one is needed.

Staying in touch with your body

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

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