Dark or Black Period Blood: Causes and What to Do About It

Dark or black period blood will often cause many women to worry because they are used to menstrual blood being deep red color. Thankfully, the appearance of dark brown, almost black spots connected with your menstrual period is not usually a sign that something is wrong. In fact, many women experience some black or dark spotting especially toward the end of their period.

There are, however, other reasons why you can have black period blood or dark spotting before or after your period. Sometimes, an irregular menstrual cycle, using birth control, and approaching the menopause can all result in dark or black blood around the time of your period. In some cases, symptoms accompanying black period blood could mean that it is best to speak to your doctor about the abnormal menstrual bleeding.

In this article, you will learn about the reasons your period blood can be dark brown or almost black. You will also find out what to do if you notice very dark period blood that is unusual in your menstrual cycle.

Why Can Period Blood be Black or Very Dark?

Your menstrual cycle lasts on average 28 days and your period starts on the first day of the menstrual bleeding. Doctors from WebMD explain that if no fertilized egg implants itself to the uterus lining (endometrium), the lining is shed and this results in the menstrual period which is usually a red to dark red color. However, every woman’s menstrual cycle is different and not all women experience the same symptoms.1

So, what does it mean when your period blood is black? Black or very dark period blood is usually old blood that is getting passed out along with regular period blood. This in itself is not something to worry about. Doctors from the National Health Service say that on the lighter days of your period, your period blood may be black, pink, or brown.2

Researchers from the Palo Alto Medical Foundation say that brown discharge and spotting is just part of the “cleaning process” when your body gets rid of the uterus lining. Blood that has been in the uterus for longer becomes brown and will affect the color of your regular period blood.3

According to doctors from the Victoria State Government, dark period blood can be part of a normal menstrual cycle. Doctors say that vaginal bleeding during your period can range in color from bright red to dark brown.4

Therefore, when period blood is black or dark brown, it usually means that there is some old blood in the flow. Depending on the amount of menstrual blood together with old blood, period blood can range from brown to dark brown to black.

Black Period Blood at the Beginning of the Period

At the beginning of your period you may notice dark brown or black period blood which could be completely normal. This could indicate that some of your old uterine lining (your endometrium) wasn’t expelled in the previous period. This old uterine lining is expelled at the beginning of the period and appears like dark brown or black period blood.

At the first few days of your period you may also notice period blood clots. These clots are normal and they usually have black or deep brown color.

But If you feel that something isn’t right or you have any concerns check it with your doctor.

Causes of Black Period Blood

Having dark and even black menstrual blood doesn’t always mean that there is something wrong. Let’s look at some of the reasons why period blood can be black.

End of period blood is darker

The most common reason for black period blood is that it occurs at the end of your period. Depending on your blood flow, some small bits of blood may stay in the vagina and turn brown. For example, some women experience light menstrual flow resulting in some blood not being expelled as quickly as usual.

Doctors from WebMD explain that darker menstrual blood can be part of a woman’s cycle and can appear towards the end of your period. They explain that the period blood that looks dark brown or almost black is just older blood that gets expelled at the end of menstruation.5

Irregular menstrual cycle

An irregular menstrual cycle may also be a reason why your period blood is dark or black. Irregular periods can result in changes to your menstrual flow which can result in old blood being passed during your period.

Doctors from the National Health Service report that irregular periods can be caused by fluctuations in your hormone levels, stress, or extreme changes in weight. This can cause your periods to become lighter or heavier and can affect the length of your menstrual cycle.6

If your periods become lighter and less frequent, then you may notice that you have dark brown or black period blood near the end of your period. As this type of dark brown discharge is part of your monthly cycle when the “cleaning process” happens, it is usually nothing to worry about.

However, if you have just started having irregular menstrual periods with abnormal vaginal bleeding, doctors from the Cleveland Clinic recommend making an appointment with your doctor. This is especially true if you have heavy bleeding, severe abdominal pains between periods, and offensive-smelling vaginal discharge.7

Birth control

When you start taking birth control pills you may find that you have a dark or black period in the first few months. Oral contraceptives affect your body’s hormones to prevent monthly ovulation and affect the lining of the uterus to prevent any conception and pregnancy taking place. These changes to your estrogen and progesterone levels affect your monthly cycle and can cause dark period blood.

Dr. Jane Harrison Hohner on WebMD says that some dark brown spotting can occur before your period while taking birth control pills. This happens as hormone levels drop and the dark brown blood is because the menstrual flow is very light and is exposed to more oxygen.8

Also, the Association of Reproductive Health Professionals says that some type of hormonal contraceptives can cause breakthrough bleeding. This results in dark brown vaginal spotting because of old blood in the uterus.9

However, most doctors say that dark blood spotting associated with taking birth control pills should only last for the first 3 months or so.

Uterine Fibroids

Uterine fibroids are benign growths in the uterus that can upset your regular menstrual cycle and cause dark period blood. Because uterine fibroids cause abnormal vaginal bleeding, there is a chance that blood stays in the uterus longer than it should and looks dark when it comes out.

Doctors from the Mayo Clinic say that uterine fibroids can be a reason for spotting or bleeding between periods, prolonged or painful periods, and constant pelvic pain.10 If you have any symptoms of abnormal, heavy bleeding, then you should see your doctor for a checkup. For more information please read my article about 7 warning signs you may have uterine fibroids. Ovarian cysts can also cause menstrual changes such as late periods, bleeding between periods or irregular periods, so you may also want to get familiar with these warning signs of ovarian cysts.


In the years during the menopause transition, you may experience darker periods with black or dark brown period blood. The reason for this is because your periods can become less frequent and you may have lighter menstrual flow.

Doctors from the Mayo Clinic say that in the years before menopause, your periods can become lighter or heavier, longer or shorter because ovulation becomes less regular.11 Because of these changes to your menstrual cycle, some old blood may be passed out and cause period blood to look dark or black.


In rare cases, the cause of dark period blood could be due to a cancerous growth in your reproductive system. Although the majority of cases with dark period blood are nothing to worry about, doctors from Cancer Research UK say one of the signs of womb cancer is abnormal bleeding. The bleeding could be accompanied with vaginal discharge that is very dark and has a bad smell to it.12

Doctors at Cancer Research UK reassure women that only a small number of cases of irregular bleeding is because of cancer. However, if you are post-menopausal and have vaginal bleeding or are worried about abnormal vaginal bleeding, you should see a doctor for a checkup to put your mind at rest.

For more information on womb cancer, please read my article on uterine (endometrial) cancer – symptoms, risk factors and prevention.

Pelvic Inflammatory Disease

An infection of your reproductive organs called pelvic inflammatory disease (PID) may affect your monthly cycle resulting in a black period. The disease itself doesn’t turn your period black but can cause irregularities in your menstrual cycle.

Doctors from the Office on Women’s Health say that some of the symptoms of pelvic inflammatory disease are irregular menstrual periods, smelly vaginal discharge, and pain in the pelvic region. It is important to get PID treated as soon as possible as the disease can progress and leave you infertile or experience other complications.13

Implantation Bleeding or Pregnancy

Of course, if you are pregnant, you won’t have any periods. However, implantation bleeding may cause dark brown or black spotting when you expect your period. Implantation spotting can be an early sign of pregnancy and happens to around one-quarter of women. Implantation spotting may cause dark-colored spots if you have become pregnant. When a fertilized egg attaches itself to the uterus lining, you may notice some implantation cramping pain and brown spots on your underwear.

According to the American Pregnancy Association, implantation bleeding causes spotting and discharge that is dark brown in color. Because this happens about 6 to 12 days after ovulation, you could mistake the dark spotting for the start of your period.14

However, the difference between implantation bleeding and regular period blood is that implantation bleeding is much lighter and only lasts up to two days.

During your pregnancy, you may also experience occasional dark spotting. The American Pregnancy Association says that about 20% of women experience some very light bleeding during their first trimester. The color of blood can range from brown to red and will be light.15


During pregnancy, you will experience an increase in discharge and this is completely normal and nothing to worry about. Doctors from the National Health Service say that many women lose a small amount of blood during pregnancy. Also, in the last week of pregnancy, you may experience thick mucus-like discharge with some blood.16

However, you should also mention any kind of vaginal bleeding during pregnancy to your obstetrician. In some cases, dark brown or black discharge during pregnancy could be a symptom of miscarriage. The Department of Obstetrics and Gynecology at UC Davis say that brown-colored discharge is old blood coming out. However, a miscarriage will have other serious symptoms like severe abdominal pain, passage of tissue from the vagina, and dizziness.17

If you have any symptoms of a suspected miscarriage, you should contact your doctor for a checkup.

What to Do if You Have Black or Dark Period Blood

Most cases of having a black period are just old blood that has been in the uterus too long and gets expelled through the vagina. This can often happen at the end of your normal period and can be associated with irregularities in the menstrual cycle.

Usually, there is nothing to worry about as doctors say that a dark or black period can be normal for many women. However, you should always pay attention to your menstrual cycle and menstrual flow. This will help you spot any irregularities in your period and help you decide if you need to see a doctor.

Black or Dark Period Blood – When to See a Doctor

In some cases of vaginal bleeding, it is wise to see a doctor for a checkup. Especially if you are pregnant, you should mention any type of vaginal bleeding to your doctor.

According to doctors from WebMD, you should see a doctor about vaginal bleeding in the following circumstances:18

  • You notice a big change in your menstrual cycle.
  • You have 3 or more menstrual cycles occur farther apart than 35 days.
  • Your period lasts longer than 7 days.
  • You start to experience heavy periods and lose a lot of blood.
  • You have gone through the menopause and have any kind of vaginal bleeding.

Read my other related articles:

Article Sources

  1. WebMD. Normal menstrual cycle.
  2. NHS. Periods.
  3. PAMF. Vaginal discharge.
  4. BetterHealth. Vaginal bleeding – irregular.
  5. WebMD. Menstrual blood problems.
  6. NHS. Causes of irregular periods.
  7. ClevelandClinic. Abnormal menstruation.
  8. WebMD. Birth control and some brown spotting.
  9. ARHP. Understanding menstrual suppression.
  10. MayoClinic. Uterine fibroids.
  11. MayoClinic. Perimenopause.
  12. CancerResearchUK. Womb symptoms.
  13. WomensHealth. Pelvic inflammatory disease.
  14. AmericanPregnancy. What is implantation bleeding?
  15. AmericanPregnancy. Spotting during pregnancy.
  16. NHS. Vaginal discharge and pregnancy.
  17. UCDMC. Understanding early miscarriage.
  18. WebMD. Abnormal uterine bleeding.

Healthy and Natural World