Understanding Black or Dark Brown Menstrual Blood: Causes & What It Means

Black or dark brown menstrual blood is typically old blood that has oxidized after remaining in the uterus or vagina for more than a day. This is common at the beginning or end of a period, with light flow, or when passing clots.

However, it can also signal underlying conditions:

• Implantation bleeding (early pregnancy)
• Miscarriage or ectopic pregnancy (often with pain/cramping)
• Sexually transmitted infections (chlamydia, gonorrhea)
• Uterine fibroids, endometriosis, adenomyosis
• Endometrial or cervical cancer (rare)

If dark bleeding is accompanied by pain, abnormal discharge, foul odor, fever, or occurs outside your expected period, consult a healthcare provider for evaluation.