Why Is My Period Blood Black? 8 Causes Of Black Discharge

Why Is My Period Blood Black
Medically reviewed by Dr. Mandy Liedeman


The change in color of the period can shock you, but it does not concern you in most cases. There are many reasons your period can be black. For example, blood oxidization due to delayed discharge can also cause a color change. Color changes can occur during the same cycle, or variations can occur. It can vary even in a single period or change from month to month due to hormonal changes. These changes are closely linked to other factors such as the environment, diet, and health conditions. Therefore, color changes can indicate reproductive well-being as it responds to environmental changes. We have discussed eight reasons for a dark-colored period in the following article. 

Why Is My Period Blood Black?

Black blood in period does look scary or out of the blue. However, in most cases, the reason is not concerning. Here is the list of all the possible causes behind black period blood: 

PCOS or Hormonal Changes

If you are experiencing black period blood, PCOS can be the culprit. During premenopause or polycystic ovary syndrome, changes in color from light pink discharge to red to dark brown are common. These hormonal changes can be triggered by stress and depression. It affects the uterus structure and reduces its wall thickness. This delays the cell peeling process in which the uterine layer sheds, removing dead cells. The longer this process takes to complete, the darker the color of period blood becomes due to oxidation. Hormonal changes due to thyroid problems are another challenge women face. It causes a delay in their period and black discharge. 

Cervical Cancer

In rare instances, black period blood can indicate an underlying health condition such as cervical cancer. When associated with this serious condition, black-colored irregular bleeding may occur after sex or during periods. Early-stage cervical cancer often lacks noticeable symptoms, but as it progresses, additional signs can occur. These may include:

  • Heavy, watery, bloody vaginal discharge with a foul odor
  • Irregular bleeding that can become dark brown or black
  • Fatigue
  • Longer or heavier periods
  • Pain during sex
  • Bleeding during or after sex
  • Weight loss
  • Pelvic pain
  • Difficulty urinating
  • Difficulty passing bowel movements
  • Swelling in the legs

Vaginal discharge in the early stages of cervical cancer may be white or clear but can turn dark over time. If you experience abnormal bleeding or unusual discharge, it’s important to consult with a healthcare provider timely.

You Black Period Blood Can be a Sign of Hormonal Imbalance? Consult a Doctor Now

Sexually transmitted infections (STIs)

Black period blood has been associated with sexually transmitted infections such as chlamydia and gonorrhea. Dark brown or black discharge is occasionally accompanied by other STI symptoms, including:

Left untreated, STIs can spread and cause pelvic inflammatory disease (PID), which infects the cervix, uterus, and other reproductive organs. PID complications include chronic pelvic pain and infertility.

Pelvic Inflammatory Disease (PID)

Black discharge could be a sign of PID, an infection in the uterus, ovaries, or fallopian tubes. PID often results from untreated sexually transmitted infections like gonorrhea and chlamydia but can also develop from non-sexually transmitted infections. Other symptoms of PID to watch out for include:

  • Pain in the lower abdomen
  • A foul odor coming from the vagina
  • Fever
  • Pain or bleeding during sex
  • A burning sensation when urinating

Heavy vaginal discharge of any color with a foul odor can be a symptom of these infections. Additional symptoms include bleeding during or after sexual intercourse, painful urination, pain or pressure in your pelvis, and vaginal itching. Without antibiotic treatment, these infections can lead to serious complications like chronic pelvic pain and infertility.


It is also called retained periods that cause black blood. It occurs due to the failure of blood to pass through the vaginal canal. The blood then stays in the vagina and accumulates, turning darker due to oxidization. There are various reasons behind hematocolpos blockages, including:

Oxidized Period at the Start or Last

You might have questions like “Why is my period blood black and thick?”. During the start or by the end, your blood can be delayed due to hormonal or bodily changes. Thus the longer it sits inside the body, the higher the chance it will react with oxygen and turn dark. Therefore, if you experience this change in color during the start or by the end, oxidation is the cause. So, you can sit back and relax while your vagina is cleaning it out. 

Something Stuck Inside

Some object pieces from sex toys or tampons could be the reason that is causing black blood in your period. The color change can be due to infection caused by vaginal lining irritation by objects like condoms, contraceptives, and tampons. This can also trigger other symptoms like itching, discomfort, lousy odor, swelling, slow urination, or abdominal pain. It can be life-threatening in rare cases, so check with your doctor immediately if you suspect something like that. 

Post Implant Bleeding

The black blood period can be disturbing, but it can be a sign that you have conceived. Dark brown-colored bleeding can sometimes happen in early pregnancy as a part of the implantation process. In this process, the egg takes time to embed itself in the uterus. Thus, old blood takes some time to leave the body, turning black. 

Postpartum Bleeding

You might experience black-colored blood after childbirth as a part of a process called Lochia. It is the normal process of removing leftover blood and clots. The color turns dark once the blood is oxidized and is almost black. However, in about four days, it returns to normal once the internal vaginal lining is cleaned of heavy black flow. Still, the light-colored bleeding continues until 6-8 weeks post-delivery, changing to beige yellow before stopping completely. 

Post Miscarriage Bleeding

Post-miscarriage bleeding is often accompanied by blood with clots releasing thick black discharge instead of a regular period. Miscarriage bleeding can change in color and thickness and can continue in intervals for some time after the miscarriage. This can happen in the first five months of pregnancy. It can indicate that embryo development has stopped. So, contact your healthcare provider if you experience anything similar. 

Serious Health Condition

In rare stances, it can indicate an underlying health condition, including cervical cancer or sexually transmitted infections (STI). In the case of cervical cancer, black-colored irregular bleeding can be released post-sex or during periods. Other symptoms, including fatigue, pain during sex, foul smell, pelvic pain, weight loss, and difficulty in urination, accompany it. However, these symptoms occur in the advanced stages of cervical cancer. During the early stages, discharge can be white or clear in color, which turns dark with time. In the case of STIs, black blood, itching, discharge, and foul smell, can be experienced. 

Other possible causes

Besides cervical cancer and STIs, dark brown or black period blood might indicate other underlying health issues such as endometriosis, uterine fibroids, endometrial polyps, or an ectopic pregnancy. If you notice unusual changes in your period blood color, it’s important to seek medical advice to determine the cause and appropriate treatment.

You Black Period Blood Can be a Sign of Serious Health Condition? Consult a Doctor for Diagnosis

Treatment options

If you’re concerned about black period blood or unsure of its cause, it’s crucial to visit a healthcare provider. Treatment options vary depending on the underlying cause:

  • Foreign object in the vagina: If a foreign object is stuck in the vagina, it’s essential to visit a healthcare provider to have the object removed timely.
  • Infections: Sexually transmitted infections (STIs) and Pelvic inflammatory disease (PID) are typically treated with antibiotics like clindamycin, metronidazole, tetracyclines, azithromycin, ciprofloxacin, and doxycycline. Follow all instructions your healthcare provider provides and complete the entire course of antibiotics to ensure the infection is fully cleared.
  • Missed miscarriage: While missed miscarriages may resolve on their own, most patients require immediate medical assistance. Treatment options include prescription medications or a dilation and curettage (D&C) procedure to remove remaining tissues from the uterus.
  • Retained menses: In cases of retained menses, surgery might be necessary to address the conditions causing the blockage. This helps to clear out the trapped blood and restore normal menstrual flow.
  • Cervical cancer: Cervical cancer treatment often involves a combination of surgery, chemotherapy, and radiation therapy, tailored to each patient’s specific needs. Early detection and treatment are crucial for the best outcomes.

When to Consult a Doctor

Black blood in a period can be a sign of an underlying health condition like endometriosis, uterine fibroids, etc. It can also indicate ectropic pregnancy if other symptoms, like pain, foul smell, itching, etc., accompany black blood. Therefore, it is advised to consult a doctor for proper diagnosis. 


Why does black-period blood smell?

Black-period blood can have a foul metallic smell. Post-oxidization blood smells metallic due to the presence of iron, which indicates oxidization and is nothing to worry about. But it goes away once the period has ended. 

Can stress cause black period blood?

Stress can contribute to hormonal changes in the body, affecting menstrual cycles. While stress itself may not directly cause black period blood, it can exacerbate underlying conditions like thyroid problems or perimenopause (the time before menopause). These conditions can lead to changes in the uterine lining and blood oxidation, potentially causing dark-colored menstrual blood.

Does black period blood mean infertility?

Simply experiencing black-colored period blood doesn’t necessarily indicate infertility. However, certain underlying conditions, such as Pelvic Inflammatory Disease (PID) or Polycystic Ovary Syndrome (PCOS) can lead to dark menstrual blood and may affect fertility. It’s essential to consult with a healthcare provider if you have concerns about fertility or notice changes in your menstrual blood color.

Does black period blood mean that you are pregnant?

It can be a sign of pregnancy in rare cases as it can indicate that implantation has occurred. However, not everybody experiences post-implantation bleeding. It usually occurs 10-14 days after conception; thus, blood takes some time to leave the body post-conception. This delay causes the blood color to change from dark brown to black. 

What does healthy period blood smell like?

The metallic smell is also present in healthy period blood, with a slight odor of blood. It is due to the presence of bacteria and iron. 

Are big black blood clots normal during the period?

During heavy period days, blood flow with clots is normal. Most women experience this at some point in their lives, and it indicates older and oxidized blood. However, it can be a matter of concern, so getting a consultation from your doctor is a safe option.

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