BV vs Yeast Infection vs STI — How to Tell Them Apart

A lot of vaginal symptoms — discharge, itching, odor — overlap between conditions that need very different treatments. The wrong treatment doesn't help and sometimes makes things worse (treating yeast won't help BV, OTC antifungal won't touch trichomoniasis, antibiotics for everything kills the good bacteria too).

Here's a clear side-by-side.

The short answer

What is BV (bacterial vaginosis)?

BV is the most common cause of abnormal vaginal discharge in people with vaginas of reproductive age. It's an imbalance — the normal lactobacilli decrease, anaerobic bacteria like Gardnerella and Atopobium overgrow.

Symptoms:

• Thin, watery, gray-white discharge
• Distinctive fishy odor — strongest after sex
• Mild itching or none
• Sometimes mild burning with urination

Risk factors:

• New or multiple sex partners
• Douching
• Lack of condom use
• Smoking
• Sometimes occurs without any sexual activity

Diagnosis:

• Vaginal pH > 4.5 (more alkaline than normal)
• Microscopy showing "clue cells"
• Whiff test (fishy odor when KOH is added)
• Or a single NAAT test that detects BV-associated organisms

Treatment:

• Oral metronidazole 500 mg twice daily for 7 days
• Or vaginal metronidazole gel 0.75% once daily for 5 days
• Or oral tinidazole 2 g daily for 2 days

Note: BV often recurs. About 50% of women have a recurrence within a year. Don't blame yourself — the microbiome is unstable.

What is a yeast infection?

A vaginal yeast infection is overgrowth of Candida (usually Candida albicans) in the vagina or vulva. Not an STI — yeast lives normally in the gut, mouth, vagina, and skin. It overgrows when conditions are favorable.

Symptoms:

• Thick, clumpy, white discharge ("cottage cheese")
• Intense vulvar itching
• Redness and swelling of the vulva
• Burning with urination
• Pain during sex
• Often no significant odor

Triggers:

• Recent antibiotic use (kills good bacteria, lets yeast bloom)
• Hormonal contraception
• Pregnancy
• Uncontrolled diabetes
• Immune suppression (HIV, chemotherapy, steroids)
• Tight, non-breathable clothing
• Damp swimsuits / workout clothes worn too long

Diagnosis:

• Visual inspection
• Vaginal pH normal (≤ 4.5)
• Microscopy showing budding yeast or pseudohyphae

Treatment:

• OTC vaginal clotrimazole / miconazole (1, 3, or 7 day courses)
• Prescription oral fluconazole 150 mg single dose (very convenient)
• For recurrent yeast (4+ episodes/year): longer maintenance therapy

What is trichomoniasis?

Trichomoniasis is caused by the protozoan parasite Trichomonas vaginalis — sexually transmitted, but often missed because it isn't in routine STI panels.

Symptoms:

• Frothy, yellow-green discharge (classic description; not always present)
• Strong, sometimes musty odor
• Genital itching and irritation
• Pain during sex
• Painful urination
• Sometimes "strawberry cervix" (red spots) visible on pelvic exam
• Often asymptomatic — particularly in men

Risk:

• Multiple sex partners
• History of other STIs
• Lack of condom use

Diagnosis:

• NAAT (most sensitive)
• Wet mount microscopy
• Antigen testing

Treatment:

• Single dose of metronidazole or tinidazole 2 g orally for the female
• Recent guidelines now favor 500 mg metronidazole twice daily for 7 days for women (more effective)
• For men: still single 2 g dose works
• Partner(s) must be treated

What about chlamydia and gonorrhea?

Chlamydia and gonorrhea can cause discharge or be asymptomatic. They tend to:

• Discharge is less characteristic in appearance
• Often more urinary symptoms (burning, urgency)
• More often pelvic pain or bleeding between periods
• Require specific NAAT testing (not detected on wet mount or pH)

If your discharge pattern doesn't match BV/yeast/trich, get full STI panel done.

The pH trick

Vaginal pH is a quick diagnostic shortcut clinicians use:

• Normal vaginal pH: 3.8-4.5 (acidic, maintained by lactobacilli)
• Yeast: pH normal (3.8-4.5)
• BV: pH elevated (> 4.5, often 5-6)
• Trichomoniasis: pH elevated (> 4.5, often 5-7)
• Chlamydia/Gonorrhea: variable

OTC vaginal pH strips exist. If you test pH at home:

• pH stays normal + classic itching/clumpy discharge → probably yeast → try OTC antifungal
• pH elevated + fishy odor → probably BV → see a clinician
• pH elevated + green frothy discharge → possible trich → see a clinician

The pH test is a useful first-pass, not a substitute for proper diagnosis if symptoms persist.

What about co-infections?

You can have more than one at once. Common combos:

• BV + trichomoniasis (often go together)
• BV + yeast (less common, but possible)
• Chlamydia + gonorrhea (common, hence dual treatment)

If symptoms persist after treatment for one condition, consider co-infection.

When to see a clinician

• First-ever episode of vaginal symptoms
• Symptoms don't fit a clear pattern
• OTC antifungal hasn't worked in 3-7 days
• Severe symptoms (significant pain, fever, abdominal pain)
• Pregnancy
• Recurrent or chronic symptoms (4+ episodes/year of any of these)
• Persistent bleeding
• Pelvic pain

What NOT to do

• Don't douche — disrupts the microbiome, makes BV worse, doesn't treat anything
• Don't use vinegar, bleach, or baking soda washes — same problem
• Don't share a partner's prescription — different conditions need different drugs
• Don't keep using OTC antifungal if it isn't working — go in
• Don't ignore strong fishy odor — that's BV until proven otherwise, and untreated BV increases risk of other STIs
• Don't have sex during treatment until you and partner(s) are treated

Treatment summary

For PID, complicated infections, or recurrent issues — clinical evaluation is necessary.

Bottom line

If you have vaginal discharge that's:

• Thick, white, cottage-cheese-like + intense itching → likely yeast
• Thin, gray, with fishy odor → likely BV
• Frothy, green-yellow + irritation → possible trichomoniasis (STI — see clinic)
• Variable + burning urination + pelvic pain → possible chlamydia/gonorrhea (STI — see clinic)

OTC antifungals are reasonable for the first signs of clear yeast. Anything else really wants a clinician + appropriate testing.

For more on testing, see STI testing window periods and free STI testing options. For specific STI guides, see our chlamydia, gonorrhea, and HPV coverage.