The STI most commonly associated with green discharge is trichomoniasis, a parasite-driven infection that produces a thin, greenish or yellowish vaginal discharge with a noticeable fishy smell. Gonorrhea can also cause green-tinged discharge, particularly in men. Both infections are treatable with antibiotics, but they require different medications and have different implications if left untreated.
Trichomoniasis: The Most Common Cause
Trichomoniasis is caused by a microscopic parasite called Trichomonas vaginalis. It’s far more common than most people realize. The World Health Organization estimated 156 million new cases globally in 2020, making it one of the most widespread STIs in the world. About a third of those infections occur in Africa, followed by the Americas.
The hallmark symptom in women is a clear, white, yellowish, or greenish vaginal discharge that tends to be thin or higher in volume than normal. It often comes with a fishy odor. You may also notice itching, burning, or redness around the genitals, and urination can feel uncomfortable. Symptoms typically appear 5 to 28 days after exposure, though many people carry the infection without any symptoms at all.
Men with trichomoniasis are even less likely to notice anything. When symptoms do show up, they usually involve mild irritation inside the penis, slight discharge, or a burning feeling after urination or ejaculation. Because symptoms are often absent or subtle, the infection spreads easily between partners who have no idea they’re carrying it.
Gonorrhea Can Also Cause Green Discharge
Gonorrhea is a bacterial infection that can produce a white, yellow, or green discharge from the penis. In women, gonorrhea discharge is more often described as thick and cloudy, sometimes bloody, rather than distinctly green. Men tend to notice symptoms within about five days of exposure, while women may take up to ten days, and many women have no obvious symptoms at all.
One important distinction: gonorrhea has developed resistance to nearly every antibiotic ever used against it. There is currently only one recommended first-line treatment left, an injectable antibiotic in the cephalosporin class. This makes proper testing critical. If you’re diagnosed with gonorrhea, completing the prescribed treatment and getting retested afterward matters more than it does for almost any other common STI.
How to Tell Which Infection You Have
You can’t reliably diagnose the cause of green discharge based on how it looks. Trichomoniasis discharge tends to be thinner and accompanied by a fishy smell, while gonorrhea discharge in men is often thicker. But there’s enough overlap in color and consistency that only a lab test can confirm which infection you’re dealing with.
The standard test for both infections is a nucleic acid amplification test, which detects genetic material from the parasite or bacteria in a urine sample or swab. These tests are highly accurate and results typically come back within a few days. Your provider will often test for both trichomoniasis and gonorrhea at the same time, along with chlamydia, since co-infections are common.
How Each Infection Is Treated
Trichomoniasis is treated with an oral antibiotic. Women are typically prescribed a course taken twice daily for seven days, while men often receive a single higher dose. An alternative single-dose option exists for both. Treatment is straightforward, and the infection clears reliably when both you and your sexual partner are treated at the same time. If only one partner takes the medication, reinfection is almost guaranteed.
Gonorrhea treatment is more limited due to antibiotic resistance. The current recommendation is a single injection at a clinic. There is no reliable oral option left for gonorrhea. Because resistance continues to evolve, a follow-up test about two weeks after treatment helps confirm the infection is actually gone.
What Happens Without Treatment
Untreated trichomoniasis increases your vulnerability to other STIs, including HIV. In pregnant women, it raises the risk of preterm delivery and low birth weight. The infection won’t resolve on its own and can persist for months or years without symptoms while remaining transmissible to partners.
Untreated gonorrhea carries more severe risks. In women, it can spread to the uterus and fallopian tubes, causing pelvic inflammatory disease, which can lead to chronic pain and infertility. In men, it can cause painful inflammation in the tubes connected to the testicles. In rare cases, the bacteria enter the bloodstream and affect joints or heart valves.
Green Discharge vs. Normal Discharge
Normal vaginal discharge ranges from clear to white and changes in consistency throughout the menstrual cycle. A faint odor is normal. What’s not normal is discharge that turns green, comes with a strong or fishy smell, or is accompanied by itching, burning, or pain during sex. Any of these changes, especially green color, points toward an active infection that needs testing.
For men, any visible discharge from the penis beyond pre-ejaculate or semen is unusual and worth getting checked. A greenish or yellowish discharge paired with burning during urination is a strong signal of either gonorrhea or trichomoniasis.