Green vaginal discharge almost always signals an infection. Normal discharge ranges from clear to white and doesn’t have a strong smell. When it turns green or yellow-green, something is triggering an immune response, and the color comes from white blood cells flooding the area to fight it off. The most common culprits are trichomoniasis, gonorrhea, and chlamydia, though bacterial vaginosis and even a forgotten tampon can sometimes be responsible.
Trichomoniasis Is the Most Common Cause
Trichomoniasis, often called “trich,” is the single most likely reason for green discharge. It’s caused by a tiny parasite passed through sexual contact and is remarkably common: roughly 156 million new cases occur worldwide each year. More than half of women with trich develop noticeable vaginal discharge, which can appear green, yellow, or gray and often looks frothy or bubbly. A fishy smell is typical.
What makes trich tricky is that many people, especially men, carry it without symptoms. So you can develop green discharge seemingly out of nowhere even if your partner seems fine. If trich is diagnosed, your sexual partner needs treatment too, or you’ll likely get reinfected. Treatment is a course of oral antibiotics taken twice daily for seven days. Men typically receive a single, larger dose. Most people clear the infection within a week or two of finishing treatment.
Gonorrhea and Chlamydia
Both gonorrhea and chlamydia can produce cloudy, yellow, or green discharge, and the two infections frequently show up together. Gonorrhea tends to cause more visible discharge than chlamydia, but both can also be completely silent. Many women with either infection notice no symptoms at all until complications develop, which is why routine screening matters if you’re sexually active.
Left untreated, either infection can spread from the cervix into the uterus and fallopian tubes, causing pelvic inflammatory disease (PID). PID adds lower abdominal pain, fever above 101°F, and pain during sex to the picture. The majority of women with PID have mucopurulent (pus-containing) cervical discharge. PID can lead to lasting damage to the reproductive tract, so catching gonorrhea or chlamydia early, before they climb higher, matters a lot.
Bacterial Vaginosis
Bacterial vaginosis (BV) happens when the balance of bacteria in the vagina shifts, allowing certain species to overgrow. The classic presentation is thin, gray or white discharge with a fishy odor, but BV can occasionally produce a greenish tint, especially when it’s more severe. The fishy smell often becomes stronger after sex. BV is not sexually transmitted in the traditional sense, though sexual activity can change the vaginal environment enough to trigger it.
BV on its own isn’t dangerous in most cases, but during pregnancy it’s been linked to preterm labor and infection of the amniotic sac. If you’re pregnant and notice green, gray, or yellow discharge, that’s worth getting checked promptly.
A Forgotten Tampon or Foreign Object
It sounds unlikely, but a retained tampon is a surprisingly common cause of foul-smelling, discolored discharge. In clinical studies, over 90% of patients with a vaginal foreign body had either foul-smelling discharge, vaginal bleeding, or both. The discharge may look brownish-green and the odor is often described as unmistakably bad. Removing the object usually resolves the problem quickly, though antibiotics are sometimes needed if tissue has become irritated or infected.
What Happens at the Doctor’s Office
Figuring out the exact cause usually starts with a simple exam. Your provider will check the pH of your vaginal fluid using a small strip of pH paper. A pH above 4.5 points toward BV or trichomoniasis, since healthy vaginal pH sits below that threshold. A sample of discharge is then examined under a microscope. In trich, the parasite is sometimes visible as a moving organism on the slide. In BV, the cells have a characteristic fuzzy appearance caused by bacteria clinging to their edges.
Microscopy only catches about 50% of trich cases, though, so if the slide looks normal but your symptoms are suspicious, your provider will likely send a more sensitive lab test called a nucleic acid amplification test (NAAT). This same type of test is used to check for gonorrhea and chlamydia and is highly accurate. Results typically come back within a few days.
Why Partner Treatment Matters
For any sexually transmitted cause of green discharge, treating your partner isn’t optional. Reinfection rates are high when only one person gets antibiotics. The CDC recommends that clinicians encourage all patients with STIs to notify their sexual partners and urge them to get tested and treated. For gonorrhea specifically, health departments may actively reach out to partners, particularly when antibiotic-resistant strains are involved. Some providers offer “expedited partner therapy,” giving you a prescription or medication to pass along to your partner so they can start treatment without a separate appointment.
Green Discharge During Pregnancy
Pregnancy naturally increases vaginal discharge, so more volume alone isn’t alarming. But a shift to green, yellow, or gray is not part of normal pregnancy discharge and may indicate an infection that needs treatment. Untreated trichomoniasis and BV during pregnancy have been associated with preterm birth and, in rare cases, infection of the fluid surrounding the baby. The reassuring part is that the antibiotics used to treat these infections are considered safe during pregnancy, so early testing and treatment can prevent complications.