Black vaginal discharge: possible causes

Vaginal discharge is produced by glands in the cervix and vagina and plays an important role in maintaining vaginal health. The normal discharge of reproductive-age women is typically thin, clear, or milky white and usually does not have a strong odor. Over the menstrual cycle the quantity and quality of discharge change in predictable ways; however, changes in color — including black or very dark brown discharge — can be concerning and merit evaluation to determine cause and appropriate management.

This article reviews the physiology of vaginal discharge, describes common and uncommon causes of black (very dark brown) vaginal discharge, outlines the clinical evaluation, and summarizes management options and red flags that warrant urgent medical attention. Medical sources consulted include guidance from the American College of Obstetricians and Gynecologists (ACOG), patient information from the National Institutes of Health (NIH/MedlinePlus), and clinical summaries from the Mayo Clinic and Cleveland Clinic.

Physiology of vaginal discharge

The vaginal canal and cervix are lined by mucous-secreting epithelium and contain glands that produce mucus, bacteria of the normal vaginal microbiome (primarily Lactobacillus species), and shed epithelial cells. Together these components produce a continuous baseline vaginal fluid that:

Keeps the mucosa moist and lubricated.
Helps clear dead cells and foreign material.
Contributes to a protective low pH environment that resists pathogenic overgrowth.

Normal discharge varies with hormonal status, age, sexual arousal, ovulation, pregnancy, and medication use. For example, periovulatory (fertile window) discharge is typically clearer and more elastic, while early and late cycle discharge can be thicker and white. Menstrual blood and spotting may also mix with secretions and change their appearance (ACOG; NIH) [ACOG], [NIH/MedlinePlus].

What is “black” vaginal discharge?

In clinical practice the term “black” discharge usually refers to secretions that are very dark brown or blackish in color. This coloration most commonly results from oxidized blood: blood that has been present in the vagina for some time undergoes breakdown and darkening as hemoglobin is oxidized to hemosiderin and other pigmented products. Thus, dark-brown or black discharge frequently represents old blood rather than a distinct fluid type.

However, several distinct pathological processes can produce dark or black-appearing vaginal discharge, and the underlying etiology determines the necessary evaluation and treatment. It is important to place the finding in clinical context — menstrual history, contraceptive use, pregnancy status, presence of pain, odor, fever, and recent procedures or foreign body exposure.

Common causes of black vaginal discharge

Below are frequent and important causes of black or very dark brown vaginal discharge, with characteristic features that help differentiate them.

1. Old or oxidized menstrual blood (retained or late-cycle bleeding)

Most commonly, dark brown or black discharge reflects aged blood from the uterus or vagina. This may occur:

At the beginning or end of a menstrual period when flow is slower and blood remains in the vagina long enough to oxidize and darken.
With intermittent spotting between periods (breakthrough bleeding) where slow bleeding produces dark-brown discharge.
Following menstruation when residual blood is expelled days later as brown/black spotting.

This type of discharge is typically not associated with fever or severe pelvic pain. Evaluation centers on menstrual pattern, use of hormonal contraception, and pregnancy status (ACOG; Mayo Clinic) [ACOG], [Mayo Clinic].

2. Retained foreign body (e.g., forgotten tampon, contraceptive device fragments)

A retained tampon or other foreign body can produce chronic, malodorous discharge that may be dark if mixed with blood. Patients may report prolonged discharge following tampon use, an inability to locate a tampon string, or a history of tampon use without removal.

A retained foreign body commonly causes a foul odor and often produces a yellow-green or brown discharge that may darken with time. Examination and speculum inspection can identify and permit removal; cultures may be needed if secondary infection is present (Mayo Clinic; Cleveland Clinic) [Mayo Clinic], [Cleveland Clinic].

3. Spontaneous abortion or retained products of conception

In pregnancy, dark vaginal bleeding or discharge may indicate early pregnancy loss when degenerated products of conception are being expelled. Retained products of conception after delivery, termination, or miscarriage can cause prolonged brown/black discharge, sometimes accompanied by cramping, fever, or heavy bleeding.

Evaluation requires a pregnancy test and pelvic ultrasound; management may include medical or surgical evacuation if products are retained (ACOG; NIH) [ACOG], [NIH/MedlinePlus].

4. Ectopic pregnancy

An ectopic pregnancy can present with abdominal or pelvic pain and vaginal bleeding that may be dark if the bleeding is subacute or slow. Any woman of reproductive age with abnormal vaginal bleeding should have a pregnancy test; a positive test with pain or instability necessitates prompt imaging and gynecologic evaluation (ACOG; Mayo Clinic) [ACOG], [Mayo Clinic].

5. Cervical or vaginal lesions (including cervical polyps, neoplasia, or malignancy)

Cervical polyps can bleed intermittently and produce brown or dark discharge when the blood mixes with vaginal secretions. More concerningly, cervical cancer or vaginal malignancy can present with irregular bleeding or dark discharge, particularly in older or postmenopausal patients. Postmenopausal bleeding, including dark discharge, is an alarm symptom that requires prompt evaluation for endometrial or cervical malignancy (ACOG; NIH) [ACOG], [NIH/MedlinePlus].

6. Endometriosis or endometrial tissue shedding

Endometriosis involves implantation of endometrial-like tissue outside the uterine cavity. If endometrial tissue is located on the cervix or vagina, cyclic bleeding and dark discharge can occur. Endometriosis-related bleeding is often cyclical and accompanied by dysmenorrhea (painful periods) and pelvic pain (ACOG) [ACOG].

7. Infectious causes with necrosis or bleeding

Most infections produce characteristic colors: candidiasis typically yields white curdy discharge, trichomoniasis often causes frothy yellow-green discharge, and bacterial vaginosis produces thin gray discharge with fishy odor. However, certain severe infections or cervicitis (for example, gonorrhea or chlamydia with mucopurulent cervicitis) may cause bleeding and brown discharge if there is mucosal erosion. Rarely, necrotizing or ulcerative infections can produce dark discharge.

Trichomoniasis may cause bloody-tinged or brownish discharge in some cases due to friable mucosa, but it is more commonly yellow-green (CDC; Mayo Clinic) [Mayo Clinic].

8. Atrophic vaginitis (postmenopausal)

Decreased estrogen in perimenopause or postmenopause leads to thinning of the vaginal epithelium (atrophy) and increased susceptibility to trauma and bleeding. This can produce spotting or dark discharge in older women. Postmenopausal bleeding or dark discharge must be evaluated to rule out neoplasia (ACOG; Cleveland Clinic) [ACOG], [Cleveland Clinic].

9. Trauma

Mechanical trauma to the vaginal walls or cervix — from intercourse, instrumentation, or accidental injury — can cause bleeding that appears dark as it ages in the vagina. Patients typically report a recent event or procedure.

10. Medications and other systemic causes

Anticoagulants and some hormonal medications can cause irregular bleeding and spotting that may darken over time. Other systemic illnesses that affect clotting or cause uterine bleeding can similarly produce dark discharge.

How clinicians evaluate black vaginal discharge

A careful diagnostic approach helps differentiate benign causes from conditions that require urgent intervention.

Medical history

Key elements include:

Age and reproductive status (pregnant, postpartum, perimenopausal, postmenopausal).
Onset, duration, quantity, and pattern of discharge (e.g., relation to menses).
Color, odor, associated pain, fever, or urinary symptoms.
Recent tampon use, intrauterine device (IUD) insertion, procedures, or trauma.
Sexual history and risk factors for sexually transmitted infections (STIs).
Medications (anticoagulants, hormonal therapy), contraceptive use.
Prior gynecologic history (polyps, cervical dysplasia, endometriosis).
Systemic symptoms (weight loss, night sweats, generalized malaise).

Physical examination

Vital signs to assess for fever or hemodynamic instability.
Abdominal exam for tenderness or guarding.
Speculum exam: visualize the cervix and vaginal walls, note color, lesions, active bleeding, foreign bodies, or polyps.
Bimanual pelvic exam: assess uterine size, adnexal tenderness or masses.

Diagnostic testing

Pregnancy test (urine or serum): essential in reproductive-age patients.
Vaginal pH and microscopy (wet mount) for clues to BV, trichomonas, or yeast.
NAAT (nucleic acid amplification testing) for chlamydia and gonorrhea.
Cervical cultures or point-of-care tests for trichomonas, bacterial vaginosis, or other pathogens when indicated.
Complete blood count if bleeding is significant or infection is suspected.
Pelvic ultrasound to evaluate for retained products, ectopic pregnancy, polyps, fibroids, or masses.
Colposcopy and cervical biopsy if a suspicious lesion is present on the cervix.
Endometrial sampling (biopsy) in older women or when abnormal uterine bleeding is of concern (ACOG) [ACOG].

Management by cause

Treatment depends on the identified or suspected diagnosis.

Oxidized menstrual blood / anovulatory bleeding

If bleeding is mild and consistent with beginning or end of menses, expectant management is often appropriate.
For heavy or prolonged bleeding, evaluation for causes (fibroids, bleeding disorders, hormonal imbalance) may be needed. Hormonal therapies (combined estrogen-progestin, progestin-only options, or levonorgestrel IUD) are commonly used to regulate bleeding per ACOG recommendations (ACOG) [ACOG].

Retained foreign body

Removal of the foreign body (tampon, condom, retained sponge) is required; this is often accomplished in the office with speculum examination and forceps.
If secondary infection is present, antibiotics may be provided. Tetanus prophylaxis is not typically required unless there is a specific indication.

Pregnancy-related bleeding or retained products

For a positive pregnancy test with bleeding, ultrasound evaluation is indicated to differentiate intrauterine pregnancy, miscarriage, or ectopic pregnancy.
Retained products of conception may require medical management (misoprostol), uterine aspiration, or surgical evacuation depending on clinical stability and local protocols (ACOG; NIH) [ACOG], [NIH/MedlinePlus].

Infections

Bacterial vaginosis: recommended treatment is metronidazole oral or topical per CDC and ACOG protocols. BV typically does not cause black discharge but can coexist with other issues (CDC; ACOG).
Trichomoniasis: single-dose oral metronidazole or tinidazole is effective; sexual partners should be treated to prevent reinfection (CDC; Mayo Clinic).
Candidiasis: topical azoles or a single oral dose of fluconazole; discharge is typically white, but mixed infections can alter appearance.
Cervicitis due to chlamydia or gonorrhea: treat with appropriate antibiotics per updated guidelines; confirm with NAAT.

Cervical or vaginal lesions and neoplasia

Polyps: office removal and histologic evaluation as indicated.
Suspicious cervical lesions: colposcopy with biopsy for definitive diagnosis.
Confirmed malignancy: management may include surgery, radiation, and/or chemotherapy depending on stage and pathology. Postmenopausal bleeding or dark discharge warrants expedited evaluation to exclude endometrial or cervical cancer (ACOG; NIH) [ACOG], [NIH/MedlinePlus].

Endometriosis

Management includes analgesics, hormonal suppression (combined oral contraceptives, progestins, GnRH agonists), and surgical options such as laparoscopic excision of lesions for symptom control and fertility considerations (ACOG) [ACOG].

Atrophic vaginitis

Topical vaginal estrogen therapy (creams, rings, tablets) often alleviates atrophic symptoms and reduces friability and bleeding in postmenopausal women. Providers should evaluate abnormal bleeding in this population to exclude malignancy (Cleveland Clinic; ACOG) [Cleveland Clinic], [ACOG].

When to seek urgent care

Black or dark discharge is not always an emergency, but certain signs require prompt medical attention:

Positive pregnancy test accompanied by pain, dizziness, fainting, or heavy bleeding (concern for ectopic pregnancy or incomplete abortion).
Fever, severe pelvic pain, or signs of sepsis.
Heavy bleeding with lightheadedness or syncope.
Foul-smelling discharge accompanied by fever or pelvic tenderness (possible retained foreign body with infection or pelvic inflammatory disease).
Postmenopausal bleeding or any new bleeding in a postmenopausal woman.
Suspected foreign body that cannot be located by the patient or is associated with severe symptoms.

If any of these occur, contact a clinician or emergency services promptly (Mayo Clinic; ACOG) [Mayo Clinic], [ACOG].

Prevention and self-care

Although not all causes are preventable, several measures can reduce the risk of problematic discharge:

Avoid douching: douching disrupts the normal vaginal flora and pH and increases risk of infections (ACOG; NIH) [ACOG], [NIH/MedlinePlus].
Follow safe tampon use: change tampons regularly (every 4–8 hours), and avoid leaving tampons in place after menses ends. Be mindful of strings and the presence of tampons; if a tampon is retained or cannot be located, seek care.
Safe sexual practices: use barrier methods and engage in mutually monogamous relationships or get regular STI screening when indicated to reduce STI risk.
Routine gynecologic care: regular cervical cancer screening (Pap tests and HPV testing at recommended intervals) and prompt evaluation of abnormal bleeding or discharge.
Vaccination: HPV vaccination reduces the risk of cervical cancer and some vulvar/vaginal cancers (CDC recommendations).
Manage chronic medications and anticoagulants with a clinician if bleeding tendencies arise.

Frequently asked questions (clinical)

Q: Is black vaginal discharge always a sign of a serious condition? A: No. The most frequent cause is old, oxidized blood associated with normal menstruation or spotting. However, persistent dark discharge, especially with symptoms (pain, fever, foul odor) or in postmenopausal women, requires medical evaluation to exclude infection, retained foreign body, pregnancy complications, or neoplasia (ACOG; Mayo Clinic) [ACOG], [Mayo Clinic].

Q: Can menstrual blood appear black? A: Yes. Slow-flow or residual menstrual blood oxidizes and darkens, often appearing brown or black, especially at the beginning or end of a period.

Q: Could an STI cause black discharge? A: Most STIs produce distinct types of discharge, but STIs that cause mucosal bleeding or erosion (e.g., gonorrhea, chlamydia) could result in dark discharge if blood is present and has oxidized. Trichomoniasis sometimes leads to brownish discharge but is more typically yellow-green (CDC; Mayo Clinic) [Mayo Clinic].

Q: What tests will my clinician order? A: Common tests include a pregnancy test, pelvic exam with speculum inspection, vaginal pH and wet mount microscopy, NAATs for chlamydia and gonorrhea, cultures or antigen testing for other pathogens, pelvic ultrasound, and biopsy or endometrial sampling when indicated (ACOG) [ACOG].

Clinical scenarios and decision points

Reproductive-age woman with short-lived dark spotting after menses and no other symptoms: observation is reasonable, with instruction to return if symptoms persist or worsen.
Woman of reproductive age with dark bleeding and positive pregnancy test: urgent ultrasound to exclude ectopic pregnancy or retained products.
Woman reporting prolonged malodorous dark discharge and history of tampon use: office exam and speculum inspection for foreign body removal and culture-guided antibiotics if infection is present.
Postmenopausal woman with any vaginal bleeding or dark discharge: expedited evaluation, including pelvic ultrasound and endometrial sampling to exclude malignancy (ACOG) [ACOG].

Summary

Dark brown or black vaginal discharge most often represents oxidized blood from menstrual or spotting events. Nonetheless, a broad differential diagnosis includes retained foreign bodies, pregnancy-related complications, infections, cervical or vaginal lesions, endometriosis, atrophic vaginitis, and trauma. The clinical context — patient age, pregnancy status, pattern of bleeding, associated symptoms (pain, fever, odor), and risk factors — guides evaluation.

Appropriate assessment typically includes a pregnancy test, pelvic examination, targeted laboratory testing (wet mount, NAATs), and pelvic imaging or tissue sampling when indicated. Management ranges from simple removal of a retained tampon and expectant care to antibiotic therapy for infection or surgical and oncologic treatment for neoplasia. Red-flag symptoms — severe pain, heavy bleeding, fever, syncope, or bleeding in postmenopausal women — require urgent medical attention.

For individualized advice and definitive diagnosis, consult a healthcare provider or an OBGYN. Timely evaluation ensures appropriate treatment and reduces risk of complications.

References

American College of Obstetricians and Gynecologists (ACOG). Practice Bulletins and clinical guidance on abnormal uterine bleeding, management of miscarriage, and related gynecologic conditions. Available at: https://www.acog.org [ACOG clinical practice resources]
National Institutes of Health — MedlinePlus. Vaginal Discharge. https://medlineplus.gov/ency/article/003150.htm [NIH/MedlinePlus]
Mayo Clinic. Vaginal discharge: When to worry. https://www.mayoclinic.org/diseases-conditions/sexual-health/in-depth/vaginal-discharge/art-20047282 [Mayo Clinic]
Cleveland Clinic. Vaginal bleeding in postmenopausal women: causes and evaluation. https://my.clevelandclinic.org/health/diseases/9663-abnormal-vaginal-bleeding [Cleveland Clinic]

(These sources provide patient and clinician-oriented information on vaginal discharge, abnormal bleeding, and recommended evaluation and management strategies.)