Why Is There Black Stuff Coming Out of My Vagina?

Black or very dark brown vaginal discharge is almost always old blood. When blood stays inside the uterus or vaginal canal long enough before exiting, it oxidizes and shifts from bright red to dark brown or black. This is the same process that turns a fresh cut’s blood dark on a bandage left in place overnight. While the color can be startling, the explanation is usually straightforward, though the underlying reason the blood was delayed in the first place ranges from perfectly normal cycle timing to conditions worth discussing with a doctor.

How Blood Goes From Red to Black

Fresh blood is red because of hemoglobin, the oxygen-carrying molecule inside red blood cells. When blood sits in a low-oxygen environment like the uterus or upper vaginal canal, hemoglobin loses its bound oxygen and undergoes chemical changes that darken it progressively. A small amount of menstrual blood that pools briefly might come out dark red or brown. Blood that has been sitting for hours or days can appear nearly black by the time it reaches your underwear. The longer it takes to travel out of your body, the darker it gets.

This is why the very beginning and very end of a menstrual period often produce the darkest discharge. At the start, remnants from the previous cycle that have been lingering in the uterus finally shed. At the tail end, the flow slows to a trickle and what little blood remains takes its time leaving. Both scenarios give blood ample opportunity to oxidize, producing that alarming dark appearance.

Normal Cycle Patterns That Produce Dark Discharge

If the dark or black discharge shows up in the day or two before your period fully starts, or during the last day or two as it tapers off, it is almost certainly just old menstrual blood. Many people notice a smear of very dark discharge on a liner a day before the real flow begins. That is leftover endometrial tissue making its way out slowly. Similarly, after the heavier days of bleeding, a day or two of dark brown to black spotting is common and not a sign of anything going wrong.

Mid-cycle spotting can also appear dark. Around ovulation, a small amount of bleeding sometimes occurs due to the hormonal shift that triggers egg release. Because mid-cycle spotting tends to be light, the blood moves slowly and oxidizes before you see it. The same can happen during implantation bleeding early in pregnancy, when a tiny amount of blood is released as a fertilized egg attaches to the uterine lining. In both cases, the small volume and slow transit explain the dark color.

Hormonal Contraceptives and Breakthrough Bleeding

If you are using a progestin-only method like an implant, hormonal IUD, or injectable contraceptive, irregular spotting and breakthrough bleeding are among the most common side effects. This bleeding tends to be light and unpredictable, which means the blood often sits in the uterus or vaginal canal for a while before making an appearance. The result is discharge that looks dark brown or black rather than the brighter red of a normal period.

Research into why progestin-only methods cause this irregular bleeding points to changes in the blood vessels of the uterine lining. In users of the Norplant implant, for instance, women who experienced breakthrough bleeding had significantly weaker structural support around their endometrial blood vessels compared to those without bleeding problems.¹ When the vessels lack adequate structural integrity, small amounts of blood can leak unpredictably into the uterine cavity and then trickle out slowly, arriving dark.

There also appears to be an oxidative stress component. In progestin-only contraceptive users, blood levels of a marker of cell-damaging oxidation were significantly higher than in women with normal cycles, while protective vitamin E levels were significantly lower.² This imbalance can damage endometrial cells and weaken the blood vessel growth response, contributing to the erratic, slow bleeding that shows up as dark discharge. Changes in how endometrial cells regulate clotting and tissue breakdown may also play a role.³

Breakthrough bleeding is the single biggest reason people stop using progestin-only contraception, so if you are dealing with persistent dark spotting on one of these methods, you are far from alone. It does not mean the method is failing or that something is wrong with your uterus. But if it is bothering you enough to consider switching, that is a reasonable conversation to have with your provider.

Retained Blood and Structural Causes

Sometimes the issue is not how the blood was produced but where it got stuck. If menstrual blood cannot drain properly from the uterus, it pools, oxidizes, and eventually comes out very dark or black. The medical term for a uterus filled with trapped blood is hematometra. It can happen when the cervix narrows or closes off, a condition called cervical stenosis. This is most commonly seen after menopause, when tissue atrophy can cause the cervical opening to shrink, but it can also follow certain procedures, radiation therapy, or be caused by growths blocking the outflow path.⁴

In younger people, a retained foreign body is another possible cause of very dark or foul-smelling discharge. A forgotten tampon is the classic example. When a tampon stays in the vaginal canal beyond its intended use, it traps blood and creates a warm, moist environment that promotes bacterial growth. The result can be dark, sometimes blackish discharge with a strong unpleasant odor. If you suspect a retained tampon or another object, a clinician can remove it quickly and treat any resulting infection.

Structural variations present from birth, such as a vaginal septum (a wall of tissue partially dividing the vaginal canal), can also trap menstrual blood on one side. Blood that drains from the obstructed side will have been sitting longer, so it tends to appear very dark. These conditions usually become apparent in adolescence when periods begin and menstrual blood has no clear exit.

Fibroids and Polyps

Uterine fibroids and cervical or endometrial polyps are benign growths that can cause abnormal vaginal bleeding. Fibroids are muscular growths in the wall of the uterus, and depending on their location, they can distort the uterine cavity and lead to heavier or prolonged periods. Polyps are softer tissue growths that dangle from the cervix or endometrial lining. Both can cause spotting between periods, and because that spotting is often light and slow, it frequently appears dark brown or black by the time you notice it.

In some cases these growths can cause significant bleeding problems. A case report described a young woman with a large cervical fibroid polyp who presented with abnormal vaginal bleeding severe enough to leave her with dangerously low blood counts.⁵ That is an extreme example, but it illustrates that growths which start as a nuisance can occasionally become a real health concern. Most fibroids and polyps are not dangerous, but persistent dark spotting that does not match your normal cycle pattern is worth bringing up with a doctor, who can check for structural causes with an ultrasound or other imaging.

Bleeding Disorders

Most people associate bleeding disorders with bruising easily or bleeding too long from cuts, but one of the most common symptoms in women with conditions like von Willebrand disease is heavy menstrual bleeding. Roughly 80 to 90 percent of women with von Willebrand disease experience abnormally heavy periods, making it one of the top reasons they seek medical care.⁶ Heavy bleeding does not always look heavy in the traditional sense. If the blood pools and drains slowly, it can come out as large dark clots or very dark discharge rather than a dramatic red flow.

A clue that a bleeding disorder might be involved is the presence of blood clots larger than about the size of a coin, periods lasting more than seven days, or the need to change pads or tampons more frequently than every hour. If any of those ring true and the dark discharge comes with patterns like this, a blood test for clotting factors is worth requesting. Von Willebrand disease in particular is underdiagnosed in women because heavy periods are often dismissed as normal variation.

When the Dark Discharge Is Not Blood

Not all dark vaginal discharge is old blood, though that is by far the most common explanation. Infections can sometimes produce discharge that appears dark or has dark streaks. Bacterial vaginosis, a common imbalance in vaginal bacteria, typically causes grayish-white discharge with a fishy odor, but in some cases, especially if there is also some bleeding from irritated tissue, the discharge can take on a darker hue. Sexually transmitted infections like chlamydia or gonorrhea can cause cervical inflammation that leads to spotting, and that blood, mixed with abnormal discharge, can look brown or nearly black.

Cervical or endometrial cancer can also cause dark or irregular vaginal bleeding, particularly in postmenopausal women who have stopped having periods altogether. Any vaginal bleeding after menopause deserves prompt evaluation, no matter the color. In premenopausal women, cancers of the reproductive tract are far less common, but persistent abnormal bleeding that does not fit any obvious pattern should still be checked.

Vaginal Hygiene Practices and Discharge Color

Some people notice dark discharge and immediately reach for douches or other internal cleaning products, thinking the darkness means something is dirty or infected. Douching does not help and can make things worse. A pilot study found that for women who douched primarily to cleanse after menstruation, stopping that practice significantly reduced their odds of developing bacterial vaginosis.⁷ The vagina is self-cleaning, and introducing fluids or products internally disrupts its bacterial balance, which can actually create the infections and abnormal discharge you were trying to prevent.

External washing with warm water and, if desired, a mild unscented soap is all that is needed. Dark discharge that is simply old menstrual blood does not indicate poor hygiene. If the discharge has a strong or foul odor alongside its dark color, that is more likely a sign of a retained object or bacterial imbalance than of insufficient washing.

What the Color and Texture Actually Tell You

The shade of dark discharge carries some practical information, though it is not a diagnostic tool on its own. Here is a rough guide to what different presentations tend to mean:

Dark brown: The most common version. Usually old menstrual blood at the beginning or end of a period, or light mid-cycle spotting that took time to exit.
Black and thick or clotted: Blood that has been sitting in the uterus for a prolonged time. Can occur after a missed or very late period, or with conditions that trap blood like cervical stenosis.
Black and foul-smelling: A retained foreign body (often a forgotten tampon) or an infection. The odor is the key signal that bacteria are involved.
Dark with gritty texture: Occasionally, endometrial tissue fragments come out as small, dark, gritty-feeling pieces. This can happen during a heavier shed, after a miscarriage, or in conditions where the lining has built up more than usual.

None of these presentations is automatically an emergency, but the presence of a strong odor, fever, pelvic pain, or discharge that persists for more than a few days outside your expected cycle is worth a call to your healthcare provider.

Dark Discharge During and After Pregnancy

Pregnancy adds a few specific scenarios that can produce very dark vaginal discharge. In early pregnancy, implantation bleeding can appear as dark brown or blackish spotting, typically showing up about a week after conception. Because the amount of blood is small and the cervix is tightly closed, it exits slowly and darkens along the way. This is normal and resolves on its own.

After delivery, vaginal bleeding called lochia continues for several weeks as the uterus heals. The flow starts heavy and red, then gradually transitions to pink and eventually to a brown or dark brown discharge before stopping altogether. Occasionally, a gush of darker blood occurs when the uterus contracts and expels a pocket of blood that had been sitting for a while. As long as the volume is not soaking through a pad in an hour and there is no fever, this intermittent dark discharge is part of the normal postpartum healing process.

A more concerning scenario is a missed miscarriage, where the pregnancy has stopped developing but the tissue has not yet been expelled. When it does begin to pass, the blood may be very dark because it has been in the uterus for days or weeks. Dark bleeding accompanied by cramping in early pregnancy warrants an urgent visit to confirm what is happening with the pregnancy.

Perimenopause and Postmenopause

During the years leading up to menopause, cycles become erratic. You might skip a month, then have a heavier-than-usual period, then spot lightly for two weeks. With all that irregularity, blood has plenty of opportunities to sit in the uterus longer than usual, producing dark discharge that looks different from anything you experienced during more regular cycling years. Fluctuating estrogen and progesterone levels also cause the uterine lining to build unevenly and shed unpredictably, which can yield tissue fragments mixed with old blood.

After menopause, any vaginal bleeding or dark discharge is considered abnormal and should be evaluated. While the cause is often benign, such as atrophic changes to the vaginal or uterine tissue, postmenopausal bleeding can also signal endometrial hyperplasia or endometrial cancer. Cervical stenosis, as mentioned earlier, is another postmenopausal cause: the cervix narrows, traps blood or fluid in the uterus, and then releases it as a dark or blackish discharge when the pressure builds enough to push past the narrowing.⁴ An ultrasound can usually sort out whether fluid is accumulating behind a narrowed cervix.

When To See a Doctor

Dark discharge on its own, especially around your period, rarely requires urgent care. But certain accompanying features shift the picture. You should contact a healthcare provider if the dark discharge comes with a foul odor that does not go away with normal external hygiene, if you have pelvic pain or cramping outside your period, if you develop a fever, if the discharge persists for more than a week without an obvious cycle-related explanation, or if you are postmenopausal and experience any vaginal bleeding at all.

It is also worth flagging if you have very heavy periods with large clots and have never been tested for a bleeding disorder. Given how often conditions like von Willebrand disease go undiagnosed in women, asking about clotting factor testing is a reasonable step if heavy, dark, clotty periods are your norm rather than the exception. A clinician can usually get a preliminary answer with a simple blood draw.