Black vaginal discharge may look alarming, but it isn’t always a reason for concern. You may see this color throughout your cycle, usually around the time of your regular menstrual period.

When blood takes extra time to exit the uterus, it oxidizes. This can cause it to appear a shade of brown to dark brown or black in color. It may even resemble coffee grounds.

There are some cases, though, where black discharge is a reason to see a doctor. Here are the symptoms to watch for.

Your menstrual flow may be slower at the beginning and end of your period. As a result, the blood in your uterus may take longer to exit your body and change from the standard red to a dark brown or black. If you see black spotting before your period, it may also be blood left over from your last period.

In these cases, your vagina is simply cleaning itself out.

Black discharge may be a sign that a foreign object is stuck in your vagina. This can happen if you accidentally put in a second tampon or forget about one at the end of your period.

Other common objects that may get stuck in the vagina include condoms, contraceptive devices like caps or sponges, and sex toys. Over time, the object irritates the lining of your vagina and may cause an infection.

Other symptoms you may experience:

  • foul-smelling discharge
  • itching or discomfort in and around the vagina
  • swelling or rash around the genitals
  • trouble urinating
  • fever

Objects can’t get lost or travel to the uterus or abdomen. Your cervix, which is located at the top of the vaginal canal, has only a small opening. That said, if you’re experiencing black discharge or other symptoms and suspect you may have something stuck in your vagina, see a doctor. In rare cases, you may develop toxic shock syndrome, a potentially life-threatening infection.

Sexually transmitted infections (STIs), like gonorrhea or chlamydia, may cause bleeding and unusual discharge. Black discharge may mean that older blood is leaving the uterus or vaginal canal. Heavy vaginal discharge of any color with a foul odor is also a symptom of these infections.

Other symptoms include:

STIs don’t go away on their own. Without antibiotic treatment, they may spread from the vagina to your reproductive organs, causing PID.

The symptoms of PID are similar to those of other STIs, but you may also experience fever with or without chills. If left untreated, PID may lead to complications like chronic pelvic pain and infertility.

Bleeding in early pregnancy is common, especially around the time of a late or missed period. You may bleed as part of the implantation process, when the egg embeds itself in the uterine lining approximately 10 to 14 days after conception. If the blood takes some time to travel out of the vagina, it may look black.

Other signs of early pregnancy include:

Not all women experience implantation bleeding, and any bleeding you experience should be light. If the spotting or bleeding you have develops into a heavy flow or lasts longer than a few days, see a doctor.

Black spotting and bleeding may also be a sign of a missed miscarriage, which is when the embryo stops developing but isn’t expelled by the body for four weeks or more. Between 10 and 20 percent of pregnancies may end in miscarriage. Most happen before the fetus reaches 10 weeks’ gestation.

You may not have symptoms with a missed miscarriage. In fact, some people don’t discover the miscarriage until they have a routine ultrasound.

Others report a loss of pregnancy symptoms, cramping, or feeling faint, among other symptoms.

Bleeding that occurs four to six weeks after delivering a baby is known as lochia. The bleeding may start out as a heavy red flow with small clots and slow within a few days. From about the fourth day onward, the lochia changes from red to pink or brown in color. If the flow is especially slow, the blood may even turn dark brown or black.

Over time, the color should change again to creamy or yellow before stopping completely.

Be sure to tell a doctor if you experience any bright red blood, clots larger than a plum, or foul-smelling discharge in the weeks after giving birth.

Retained menses (hematocolpos) happens when menstrual blood is blocked from leaving the uterus, cervix, or vagina. As a result, the blood may turn black over the time it’s retained. The blockage may be caused by anything from a congenital issue with the hymen, vaginal septum, or in rare cases absence of a cervix (cervical agenesis).

Some people don’t experience any symptoms. Others find that symptoms are cyclical and occur in place of an expected menstrual cycle.

If the blockage is particularly severe, you may develop amenorrhea, or a complete lack of menstruation. Other complications include pain, adhesions, and endometriosis.

In rare cases, black discharge may be a sign of cervical cancer. Although many people don’t have any symptoms, irregular bleeding between cycles or after sex is the most common sign of invasive cancer.

Vaginal discharge in early cancer may be white or clear, watery, or foul smelling. It can even be streaked with blood that over time may turn dark brown or black as it exits the body.

In more advanced stages of cervical cancer, you may experience:

  • weight loss
  • fatigue
  • pelvic pain
  • swelling in your legs
  • trouble urinating or defecating

Black discharge may be a part of your menstrual cycle and require no special treatment. When the discharge is heavy and accompanied by other symptoms, like fever, pain, or a bad odor, it’s a good idea to see a doctor.

The treatment for black discharge depends on the cause. For example:

  • Objects in the vagina should be removed by a doctor, especially if you’re experiencing symptoms like black discharge, pain, or fever.
  • Infections like PID are managed by antibiotics. Follow all instructions from your doctor and take measures to protect yourself from reinfection, like practicing safe sex.
  • Missed miscarriage may eventually resolve on its own. If not, your doctor may suggest a dilation and curettage (D&C) procedure. In this procedure, your doctor uses medical instruments and medication to dilate your cervix while you’re under anesthesia. A surgical instrument called a curette is then used to remove any tissue.
  • Retained menses may require surgery to treat any underlying conditions that led to blockage.
  • Treatment for cervical cancer may involve surgery, radiation, chemotherapy, or a combination of these treatments.

Black discharge at the start and end of your period usually isn’t a reason to worry.

A typical period may last anywhere from 3 to 10 days and happen every 3 to 6 weeks. Periods can be different from month to month. Bleeding or seeing black discharge outside this general time frame is considered irregular and should be discussed with a doctor.

If you’re pregnant or have recently delivered a baby, contact a doctor if you see black discharge. You should seek immediate medical attention if you’re experiencing other unusual symptoms, like fever or cramping.

You should also see a doctor if you’ve reached menopause but begin to experience black discharge or other unexpected bleeding. This may be a sign of a serious underlying condition.