Black period blood is usually old blood that has taken longer to exit the uterus, causing it to oxidize and darken, often seen at the beginning or end of a period when flow is slow. Common causes include slow shedding of the uterine lining, hormonal changes (like in perimenopause or PCOS), blocked cervical flow (cervical stenosis), or old blood from a previous cycle. While often normal, seek medical advice if it's accompanied by severe pain, fever, foul odor, or if it's a new, concerning change, as it could signal infection (like PID) or a miscarriage.
The phenomenon of black menstrual blood is mainly due to the condition of menorrhagia, menstrual blood stagnates for many days in the uterus before coming out. If this condition occurs for a long time without seeking treatment, it can affect fertility later.
Periods that stop and start again can be caused by hormonal changes, stress, or irregular ovulation. Learn more about the reasons for intermittent bleeding and find out when to consult a doctor.
A stress period looks like menstrual changes due to hormonal disruption, featuring spotting, early/late/missed periods, heavier/lighter flow, longer duration, bigger clots, more cramping, worse PMS, and potential loss of libido, alongside physical signs like headaches, fatigue, muscle tension (neck/back pain), jaw clenching, and digestive issues, all stemming from elevated cortisol and disrupted reproductive hormones.
In many cases, black blood during a period is a normal variation of your menstrual flow. This color change is especially seen at the beginning or end of a menstrual cycle when the flow is lighter and moves more slowly. However, if other symptoms accompany black period blood, that could indicate an underlying condition.
Myth: Black period blood means infertility. Fact: While conditions like PCOS, which may cause dark blood, can affect fertility, the appearance of black blood alone does not determine reproductive capability.
Key Takeaways. Bright red period blood is common at the start of your period and indicates blood has passed through your vagina quickly. Orange, gray, or green tinges in period blood can be signs of an STI or other infection.
PCOS causes dark period blood due to: Infrequent periods – With PCOS, periods may be delayed, leading to old blood accumulating and turning black. Thickened uterine lining – Since periods are irregular, the lining builds up over time, causing heavier or darker bleeding when it sheds.
Anaemia, a condition caused by low iron levels, can also cause pink period blood.
A woman's menstrual cycle actually lasts around 28 days on average but can be between 21 and 35 days, and it consists of four phases: menstruation, follicular, ovulation and luteal.
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.
Now, some women think black period blood is a sign of pregnancy. And, while that's not usually the case, it could be a sign of a miscarriage or ectopic pregnancy. (Since fibroids during pregnancy can increase your risk for miscarriage, this is a critical symptom to mention to your OBGYN.)
If you're already several weeks into a pregnancy, any persistent bleeding—whether red, brown, or black blood—may indicate a miscarriage. Missed miscarriages (also called silent miscarriages) are a type of pregnancy loss that are most commonly associated with black blood or discharge.
During your period, the flow changes speed. It can be lighter and slower at the start and end, and the blood may appear dark brown or black rather than bright red. This is because the blood has spent more time in your uterus before exiting your body. The longer it stays, the darker it may become.
Uterine fibroids or polyps can cause black period blood, which is associated with black blood clots, excessive bleeding, and severe pain. Hence, it is better to consult a healthcare professional for the same. Obstructions that block the regular flow of period blood can also cause black period blood.
You might find yourself soaking through a pad or tampon every hour. While the color is often dark red, look out for grayish tissue. A foul odor with clots can also signal an infection. Regularly passing large clots suggests an underlying issue.
Physical signs of stress
Menstrual periods typically last four to seven days and occur roughly every 28 days. Examples of irregular periods include periods that occur fewer than 21 days or more than 35 days apart, missing three or more periods in row, and menstrual flow that's much heavier or lighter than usual.
Gray Period Blood
This color is often a mixture of normal menstrual blood and gray discharge, which is a sign of certain vaginal infections like BV (bacterial vaginosis). So, if your period blood has a grayish quality, it's a good idea to call your healthcare provider and get checked out.
If you have bleeding that lasts longer than 7 days per period or is so heavy that you have to change your pad or tampon nearly every hour, you need to talk with your healthcare provider.
You might find yourself soaking through a pad or tampon every hour. While the color is often dark red, look out for grayish tissue. A foul odor with clots can also signal an infection. Regularly passing large clots suggests an underlying issue.
Brown period blood is generally normal and common. It typically occurs at the beginning or end of menstruation, indicating older blood that has had time to oxidise. However, if it persists for several weeks or is accompanied by unusual symptoms, it's advisable to consult a doctor.