The STD most commonly associated with green discharge is trichomoniasis, a parasitic infection caused by a microscopic organism called Trichomonas vaginalis. Gonorrhea can also produce green discharge, particularly in men. Both infections are curable with antibiotics, but they require different treatments and have different symptom profiles worth understanding.
Trichomoniasis: The Most Common Cause
Trichomoniasis produces a discharge that ranges from clear to white, yellowish, or greenish, often with a noticeable fishy smell. The discharge tends to be thin or higher in volume than normal. In women, it frequently comes with itching, burning, or redness around the genitals, and urination can be uncomfortable. Not everyone gets symptoms, though. An estimated 70% of people with trichomoniasis have no symptoms at all, which is one reason the infection spreads so easily.
Symptoms typically appear 5 to 28 days after exposure, but some people carry the parasite for months without knowing it. In men, trichomoniasis usually causes fewer noticeable symptoms. When it does show up, it tends to involve irritation inside the penis, mild discharge, or a burning sensation after urinating or ejaculating.
Trichomoniasis is one of the most common STDs in the United States, yet it’s often overlooked because routine STD panels don’t always include it. You typically need to ask for the test specifically.
Gonorrhea: Green Discharge in Men
Gonorrhea is the other STD that can cause green discharge, and it’s especially relevant for men. The CDC lists white, yellow, or green discharge from the penis as a hallmark symptom. This discharge is often thicker than what trichomoniasis produces and tends to appear within a few days of exposure.
In women, gonorrhea is trickier. It often causes no obvious discharge at all, or the symptoms overlap so much with other vaginal infections that it’s easy to miss. When discharge does occur, it’s more commonly yellowish. Painful urination and bleeding between periods are other signs, but many women remain asymptomatic until the infection has progressed.
How to Tell Them Apart
You can’t reliably distinguish trichomoniasis from gonorrhea based on discharge color alone. Both can produce greenish or yellowish discharge, and both can be completely silent. That said, a few patterns can help you understand what’s going on:
- Odor: Trichomoniasis often produces a fishy smell. Gonorrhea discharge typically doesn’t have the same strong odor.
- Texture: Trichomoniasis discharge tends to be thin and frothy. Gonorrhea discharge is usually thicker, sometimes resembling pus.
- Timeline: Gonorrhea symptoms generally appear faster, often within 2 to 5 days. Trichomoniasis has a wider window of 5 to 28 days.
- Who notices it: Men are more likely to notice green discharge from gonorrhea. Women are more likely to notice green discharge from trichomoniasis.
These patterns are generalizations. The only way to know for certain is through testing.
What About Bacterial Vaginosis?
Bacterial vaginosis (BV) is not an STD, but it’s worth mentioning because it causes discharge with a fishy smell that can look similar to trichomoniasis. BV discharge is usually thin and grayish-white, though it can occasionally appear off-color. One way clinicians distinguish between the two is vaginal pH: BV tends to raise pH above 4.5, while trichomoniasis pushes it even higher, above 5.4. You won’t be measuring your own pH at home, but if you’ve been told you have BV and the discharge looks distinctly green, it’s reasonable to ask about trichomoniasis testing as well.
Getting Tested
If you’re noticing green discharge, getting the right test matters. For trichomoniasis, the older method of looking at a sample under a microscope (called a wet mount) catches only 44% to 68% of infections. That means it misses roughly one in three cases. Newer molecular tests, known as nucleic acid amplification tests, are far more accurate, with sensitivity rates above 95%. If your provider uses only a microscope slide and it comes back negative, a normal result doesn’t necessarily rule out trichomoniasis.
Gonorrhea testing is more straightforward and is usually included in standard STD panels. The same type of molecular test works for both infections, and many labs can run them from a single urine sample or swab.
Because trichomoniasis and gonorrhea require different medications, knowing exactly which infection you have changes what treatment you’ll receive. Both are fully curable. Trichomoniasis is treated with a specific antiparasitic medication, while gonorrhea requires antibiotics that target bacteria. Sexual partners need to be treated at the same time to prevent passing the infection back and forth.
Why Treatment Matters
Left untreated, both infections can cause problems beyond uncomfortable discharge. Trichomoniasis increases susceptibility to HIV by creating inflammation that makes it easier for the virus to enter the body. During pregnancy, untreated trichomoniasis raises the risk of preterm birth and low birth weight. Untreated gonorrhea can spread to the reproductive organs and cause pelvic inflammatory disease in women, which can lead to chronic pain and fertility problems. In men, it can cause painful swelling in the tubes near the testicles.
Green discharge is your body signaling that something is off. The color alone doesn’t give you a diagnosis, but it narrows the list considerably. Trichomoniasis and gonorrhea sit at the top of that list, and both are straightforward to test for and treat once identified.