Green or yellow-green discharge most often points to a sexually transmitted infection, usually gonorrhea or trichomoniasis, and sometimes chlamydia. Non-STI causes like bacterial vaginosis or a yeast infection can shift discharge color too, but green is the most STI-suggestive shade. These conditions overlap and many are silent, so only a test gives you a real answer.
Neisseria gonorrhoeae
Trichomonas vaginalis
Chlamydia trachomatis
| Item | Value |
|---|---|
| Gonorrhea | curable — Neisseria gonorrhoeae |
| Trichomoniasis | curable — Trichomonas vaginalis |
| Chlamydia | curable — Chlamydia trachomatis |
What causes green discharge?
Discharge turns yellow-green when white blood cells flood the genital tract to fight an infection. That pus-like tint is your immune system at work, so a distinctly green or thick yellow-green discharge tends to signal an active infection rather than a normal fluctuation. The likely culprits:
- Gonorrhea — a bacterial STI that classically produces a thick yellow or green discharge.
- Trichomoniasis — a parasitic STI that can cause a frothy greenish discharge with a fishy odor.
- Chlamydia — usually silent, but can cause abnormal discharge when symptoms appear.
- Non-STI causes — bacterial vaginosis and yeast infections can alter discharge, though green specifically leans toward an STI.
These conditions overlap too much to tell apart by sight, and several are frequently silent. A test settles which one, if any, you have [E1].
Which STIs cause green or yellow-green discharge
Gonorrhea
Gonorrhea is caused by the bacterium Neisseria gonorrhoeae, which can infect the genitals, rectum, and throat CDC, About Gonorrhea. In men, it tends to announce itself: burning when urinating and a white, yellow, or green penile discharge, and less commonly swollen or painful testicles. That green discharge in men is one of the more recognizable presentations of any STI. In women, the picture is sneakier. Most have no symptoms, but when they do, it's painful or burning urination, increased vaginal discharge, and bleeding between periods. If you're seeing a green discharge with urinary burning, gonorrhea belongs at the top of the differential.
Trichomoniasis
Trichomoniasis comes from a protozoan parasite, Trichomonas vaginalis, and it's the most common curable STI CDC, About Trichomoniasis. It's also the classic cause of a greenish discharge with a fishy smell. About 70% of infected people have no signs or symptoms at all, so a green discharge here is the exception. When women do have symptoms, they include itching, burning, redness or soreness of the genitals, discomfort urinating, and a clear, white, yellowish, or greenish discharge. Men are commonly asymptomatic but may notice itching or irritation inside the penis, burning after urinating or ejaculating, and discharge. Reviewing the full set of trichomoniasis symptoms helps you spot the frothy, odorous discharge that distinguishes it.
Chlamydia
Chlamydia is caused by the bacterium Chlamydia trachomatis, and most US genital infections are serovars D–K CDC Chlamydia Fact Sheet. It's a 'silent' infection, with roughly three-quarters of infected women and half of infected men having no symptoms. So while chlamydia can produce abnormal vaginal discharge and burning on urination, a vividly green discharge is less typical for it than for gonorrhea or trichomoniasis. Don't rule it out. If it spreads upward, women can develop lower abdominal or low-back pain, fever, pain during intercourse, and bleeding between periods, all signs the infection has reached the upper reproductive tract.
When it's NOT an STI
Not every abnormal discharge is sexually transmitted. Two common non-STI conditions change discharge, but each has a recognizable signature:
- Yeast infection — produces a thick, white, cottage-cheese-like discharge with intense itching, not a green one.
- Bacterial vaginosis (BV) — produces a thin grey or white discharge with a distinct fishy odor, rather than a true green.
Both can look 'off' and feel alarming, but neither typically gives you the pus-like green that points toward an STI. Green is the most STI-suggestive color of the bunch, so it deserves a test rather than a guess.
How to tell them apart
You can't reliably tell by sight, and that's not a personal failing. Color, texture, and smell overlap heavily across these conditions, and the most common scenario is no symptom at all. A faint odor might suggest trichomoniasis or BV; burning with urination raises gonorrhea or chlamydia; itching points toward yeast. These clues only narrow the field. The discriminating features below are a starting framework, not a diagnosis.
| Cause | Type | Typical discharge | Other clues | Often silent? |
|---|---|---|---|---|
| Gonorrhea | Bacterial STI | White, yellow, or green; often thick | Burning urination; testicular pain (men) | Common in women |
| Trichomoniasis | Parasitic STI | Greenish/yellow, sometimes frothy, fishy odor | Genital itching, soreness | About 70% have no symptoms |
| Chlamydia | Bacterial STI | Abnormal, not classically green | Burning urination; pelvic pain if spreads | ~75% of women, ~50% of men |
| Yeast infection | Non-STI | Thick, white, cottage-cheese-like | Intense itching, redness | No |
| Bacterial vaginosis | Non-STI | Thin grey/white, fishy odor | Odor worse after sex | Sometimes |
How green discharge is tested
For all three STIs above, a nucleic acid amplification test (NAAT) is the recommended method. It's the preferred screening test for gonorrhea, with sensitivity usually over 90% and specificity around 99% CDC, Gonorrhea, the optimal method for chlamydia at genital and extragenital sites CDC STI Treatment Guidelines, 2021, and the preferred test for trichomoniasis, where assays like the Aptima reach roughly 95–100% sensitivity CDC, Trichomoniasis 2021. In practice, testing means a urine sample, a self-collected swab, or a quick exam depending on what's suspected, and it's free or low-cost at health departments, Planned Parenthood, and Title X clinics, with results usually back in a few days [E2]. You can get tested for all three from a single visit.
Timing matters: if you test too soon after exposure, an infection may not yet be detectable. Trichomoniasis symptoms, when they appear, can show up roughly 5 to 28 days after infection, sometimes much later, and chlamydia symptoms usually surface within one to three weeks. Check when to test after exposure to make sure your result is reliable.
What to do next
All three of these STIs are curable with medication, and a clinician will match the treatment to whatever the test confirms. Don't try to treat green discharge with leftover antibiotics or over-the-counter yeast products. Guessing the cause can delay treatment and let the infection spread or progress. Get tested, and if a result comes back positive, your provider will walk you through treatment and partner notification. Avoid sex until you and any partners have been treated and cleared.
Red flags — when to get seen urgently
Discharge alone usually isn't an emergency, but certain symptoms mean you should be seen promptly rather than waiting on a routine appointment:
- Fever with lower abdominal or pelvic pain — a possible sign infection has spread to the upper reproductive tract.
- Severe pelvic or low-back pain, or pain during intercourse, in someone with abnormal discharge.
- Swollen, painful testicles, which can signal infection has reached the epididymis (the coiled tube behind the testicle that stores sperm).
- Bleeding between periods alongside discharge and pain.
- Symptoms in a pregnant person, since untreated STIs can affect pregnancy and the newborn.
If you have any of these, contact a clinician or urgent care the same day rather than waiting out the discharge.