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Why is My Period Blood Black?



5 min read

Thinx Periodical Why Is My Period Blood Black

by Team Thinx | 04/03/2023

Thinx Inc - Thinx Tank - Doctors - Dr. Brandi Jones, DO

Medically reviewed by Dr. Brandi Jones, DO

If you’ve been the proud owner of a period for a while, you may have gotten to know your menstrual patterns the same way you’ve become familiar with which junk food gives you gas and how much hair you shed in the shower. Other times, certain details catch us off guard — so if black blood pops up in your undies, it’s entirely normal to feel a jolt of worry.

Yes, changes to your period blood color and duration could be indicative of something amiss — but even the darkest-looking period blood might be nothing out of the norm at all. 

Since your cycle is an intimate reflection of your overall health, we’ll examine the most common causes of black period blood below (and when it’s certainly time to book an appointment with your OBGYN.)

is black period blood normal?

Let‘s have a quick refresh: your “period” is shorthand for the sloughing away of your uterine lining after the luteal phase in your menstrual cycle.

This “shedding” is a combination of menstrual blood and tissue that can carry a variety of consistencies, from jelly-like to stringy, and different colors. Wondering why your period blood is black or brown, or what causes dark brown discharge instead of period blood? Colors can appear pink, orange, red, brown, and, yes, sometimes black.

If you do see black period blood, it will probably arrive at the beginning or end of menstruation. On other occasions, black blood can appear at the peak of your period, when your period is at its heaviest. At other times still it can emerge as brown discharge, or between your periods.

what is black period blood, exactly?

It depends on where you are in your cycle. 

Black blood that appears on the first day of your period or as your period thins out towards the end may just be old blood that has been hanging out in your uterus and vagina. While your body is a magnificent and efficient machine, not all of your uterine lining is always cast off during your period. Two things occur when blood and tissue overstay their welcome:

  1. They begin to clot

  2. The mixture is exposed to oxygen, becomes oxidized, and tends to alter its color, causing a black discharge

Sometimes, this happens because your uterus isn’t contracting as much and hasn’t discarded its lining as quickly as it did in periods past. 

Other times, black period blood flow may be indicative of an underlying health issue—a crucial topic we’ll jump into next.

when is black period blood not normal?

If you experience black period blood alongside an additional symptom, schedule an appointment with your OBGYN. Red-flag symptoms could include:

  1. Severe, worse-than-usual cramping

  2. Periods that contain quarter-sized or larger blood clots

  3. Irregular periods

  4. Heavy bleeding (like soaking through a pad or tampon every hour)

  5. Prolonged periods, or periods that last seven days or longer

  6. Trouble becoming pregnant

  7. Pain during sex

  8. Unusual, foul-smelling odors

  9. Fever

All of these symptoms, coupled with black period blood, could be a critical indicator that it’s time to screen for an underlying health condition.

what causes black period blood?

Black period blood that’s unaccompanied by other symptoms may be just part and parcel of possessing a uterus. Other times, though, it could be another reproductive health condition.

benign growths

Fibroids, polyps, and other growths can sometimes develop in your reproductive organs like your ovaries and uterus. Many are benign, but they can be cancerous in rarer cases. The Mayo Clinic asserts that most people who menstruate will experience uterine fibroid at some point in their life.

In addition to heavy menstrual bleeding and changes in the color of your period, benign growths can cause:

  1. Persistent menstrual bleeding, or bleeding that goes on for more than seven days

  2. Frequent urination

  3. Pelvic pressure and pain

  4. Constipation

  5. Aches in your legs and back

an object that… isn’t supposed to be there

Who could forget the classic SATC scene when Carrie gets a new diaphragm stuck in her vagina and Samantha — good sport that she was — helps her remove it?

Yes, it’s true: foreign objects can get stuck inside and cause dark or unusual discharge that’s easy to confuse with your period. In severe cases, they could cause an infection. The following objects get “left behind” more frequently than you might imagine:

  1. Tampons

  2. IUDs

  3. Condoms

  4. Menstrual cups

  5. Sex toys

Irritation is one of the main symptoms of a trapped foreign object. Others include:

  1. Itching

  2. Foul smell

  3. Rash in the genital area

  4. Fever

  5. Pain and/or pressure

If this is the case, it’s important to reach out to your healthcare professional immediately (no, not the Samantha Jones in your life) to ensure the abandoned object hasn’t put you at risk of infection or injury.

sexually transmitted infection (STI)

Common STIs like chlamydia and gonorrhea may cause what appears as “strange” and even dark vaginal discharge (just in case you needed another reason to prioritize regular sexual health checkups).

One of the dangers of STIs is that they can go completely unnoticed because many carriers may be asymptomatic. But if you are exhibiting symptoms, these may include:

  1. Pain during sex and/or urination

  2. Burning sensation when urinating

  3. Lower abdominal pain 

  4. Bleeding between periods

  5. Vaginal itching and irritation

  6. Fever

early miscarriage

Dark brown vaginal discharge — typically discharge that resembles coffee grounds — may be a sign of a miscarriage, a complication affecting an estimated 10 to 20% of people who menstruate. Miscarriage blood usually lingers in the uterus and may arrive with other tissue.

The usual symptoms of pregnancy — such as swollen and tender breasts — may or may not be present before an early miscarriage. People having a miscarriage may also experience:

  1. Nausea and/or vomiting

  2. Abdominal cramping

  3. Spotting, bleeding, or clots

ectopic pregnancy

Ectopic pregnancy occurs when a fertilized egg implants itself outside the uterus, typically in the fallopian tubes. This condition can lead to internal bleeding if left untreated and poses severe health risks. While black discharge or bleeding isn't the sole indicator of an ectopic pregnancy, it could be accompanied by symptoms such as:

  1. Intense abdominal pain, often concentrated on one side

  2. Abnormal bleeding, might be a dark discharge or appear as breakthrough bleeding 

  3. Shoulder pain due to internal bleeding affecting the diaphragm

  4. Weakness, dizziness, or fainting

  5. Bloating, nausea, or vomiting

If you experience black period blood alongside any of these symptoms, we recommend that you seek immediate medical attention.

cervical cancer

Although it’s rare, dark vaginal discharge can be a warning sign of cervical cancer, a disease that affects approximately 14,000 people each year. Cervical cancer can be challenging to detect, as it doesn’t always present with symptoms—and when symptoms do surface, the illness may be in its later stages. 

Fortunately, getting the HPV vaccine alongside routine health screenings may help mitigate your risk of cervical cancer. If you see black period blood along with any or all of the following, schedule an appointment with your gynecologist right away:

  1. Fatigue 

  2. Weight loss 

  3. Loss of appetite

  4. Irregular periods

  5. Swelling in your legs

  6. Diarrhea

  7. Mild back aches

  8. Painful urination (and blood in your urine)

  9. Abdominal and/or pelvic pain

  10. General malaise

other gynecological cancers

Upwards of 80,000 people who menstruate (or have gone through menopause) are diagnosed with gynecologic cancers annually; in addition to cervical cancer, these include ovarian and uterine, or endometrial, cancer. Early detection is key to all cancers, and dark discharge/black period blood color may be a sign.

other signs to be mindful of include:

  1. Frequent urination and/or bladder pressure

  2. Unexplained weight loss

  3. Appetite changes, such as feeling full right away or barely hungry at all

  4. Bloating

  5. Fatigue

  6. Nausea

  7. Indigestion

Clearly, none of this is said to frighten you; as mentioned, most black period blood isn’t anything to be worried about. But with information comes power — and keeping an eye on your period can help you stay apprised of your health and wellness overall.

is there anything you can do about black period blood?

If an underlying issue has been ruled out by your PCP or OBGYN, and you simply don’t want to experience that heart-skip of fear that coincides with spotting black period blood, it’s perfectly understandable to want to dodge it altogether.

The only problem: no one has much say over the colors and textures of their period. If you really aren’t keen on your period’s hue, making a few lifestyle tweaks may help regulate it more generally:

  1. maintaining a healthy weight — Weight plays an important role in achieving and sustaining hormonal balance. Whether you’re carrying more or less weight than your build requires, you may experience heavier, thinner, longer, or shorter periods. If you’re struggling to lose or gain weight, or suspect you may have an eating disorder, a tremendous act of self-care can be discussing it with a trusted healthcare provider.

  2. exploring hormonal birth control — Hormonal birth control pills, injections, and IUDS can further moderate your periods and may result in lighter, less clotty periods. Sometimes, they can give you a break from experiencing them altogether.

  3. practicing the pillars of health — Your head-to-toe health has a direct impact on your hormones and menstrual cycle. A balanced diet, adequate sleep, movement, and avoiding stress and toxins are all ways to support wellness overall.

Think of it this way: building up your health can be a creative act, so get experimental! Whether it’s weekly yoga practices or dinners out with your crew, discovering what makes you feel good mentally and physically can go a long way in supporting worry-free periods.

have a comfier period with Thinx

While alarming, black period blood could be nothing more than old blood that hasn’t yet budged from your uterus or vagina. If it’s coupled with other symptoms, be kind to yourself and contact your OBGYN ASAP to rule out any underlying conditions — and the mental discomfort that can come from worrying if something's wrong.

Whether you have pale pink period blood or a healthy (and kind of punk rock) black, Thinx can help your period days feel more like a breeze. Our signature underwear is made with ultra-comfortable, dry-wicking, and odor-controlling materials that help build up your confidence and a more sustainable Earth.

Dive into our Thinx period underwear collection today to discover our designs and redefine your monthly cycle.

At Thinx, we strive to provide our readers with the most up-to-date, objective, and research-based information. Our content is crafted by experienced contributors who ground their work in research and data. All information has been fact-checked and extensively reviewed by our team of medical professionals to ensure content is accurate. Articles contain trusted third-party sources that are either directly linked within the text or listed at the bottom to lead readers to the original source.


Office on Women’s Health. Your menstrual cycle and your health.

Cleveland Clinic. What does the color of your period mean?

Mayo Clinic. Uterine fibroids.

National Library of Science. Vaginal foreign body evaluation and treatment.

Mayo Clinic. Sexually transmitted diseases (STDs) symptoms

UC Davis Health. Signs of an early miscarriage.

Mayo Clinic. Vaginal discharge causes.

Cleveland Clinic. Cervical cancer: causes, symptoms, diagnosis & treatment.

Science Daily. Ten gynecologic cancer symptoms women shouldn’t ignore.

Mayo Clinic. Menstrual cycle: what’s normal, what’s not.

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