The most telling sign of bacterial vaginosis is a thin, grayish-white discharge with a noticeable fishy smell. But nearly half of people with BV have no obvious symptoms at all, which means you can have it without knowing. Understanding what to look for, and how BV differs from other vaginal infections, can help you figure out what’s going on and whether you need testing.
The Main Symptoms of BV
BV produces a distinctive set of signs that differ from other vaginal infections. The discharge is typically thin, uniform, and grayish-white to yellow. It tends to be heavier than normal and has a homogeneous, almost watery consistency rather than being clumpy or thick. The volume alone can be what prompts people to search for answers.
The smell is often the biggest giveaway. BV discharge has a characteristic fishy odor that can become stronger after sex or during your period. This happens because semen and menstrual blood both raise vaginal pH, which releases more of the odor-causing compounds produced by the overgrown bacteria. Some people notice the smell only at those times, while others detect it throughout the day.
Unlike yeast infections, BV typically does not cause significant pain, redness, or intense itching. You may feel mild irritation, but if you’re experiencing burning, soreness during sex, or swelling, that points more toward a yeast infection or another condition.
How BV Differs From a Yeast Infection
These two conditions get confused constantly, but they look and feel quite different. A yeast infection produces thick, white, cottage cheese-like discharge. BV discharge is thin and grayish. Yeast infections cause itching, burning, and pain, particularly after intercourse. BV is more about the smell and the volume of discharge than about discomfort.
The underlying cause is different too. A yeast infection is fungal overgrowth. BV is a bacterial imbalance where protective bacteria (mainly Lactobacillus species) decline and are replaced by a mix of anaerobic bacteria. The Lactobacillus normally keeps your vaginal environment acidic, which holds other microbes in check. When those populations drop, the pH rises above 4.5 and conditions shift in favor of the bacteria that cause BV symptoms.
You Can Have BV With No Symptoms
In one study of 470 people diagnosed with bacterial vaginosis, 48% were completely asymptomatic. They had the bacterial imbalance on testing but reported no unusual discharge, no odor, nothing out of the ordinary. This is important because untreated BV, even without symptoms, can increase your susceptibility to sexually transmitted infections and cause complications during pregnancy, including preterm delivery, early miscarriage, and low birth weight.
If you’re pregnant or planning to become pregnant, this is worth discussing with your provider even if you feel fine. Research on treating BV in people with a history of preterm delivery has shown reductions in preterm birth risk of 18% to 29% after treatment, though results vary.
What Raises Your Risk
Several factors make BV more likely. According to the CDC, douching is one of the strongest risk factors because it directly disrupts the vaginal bacterial balance. Having new or multiple sex partners, and not using condoms, also increase risk. Other associated factors include younger age, tobacco use, and having concurrent sexually transmitted infections.
Anything that shifts vaginal pH can trigger a flare. Semen is alkaline compared to the vagina’s naturally acidic environment, which is why some people notice symptoms appearing or worsening after unprotected sex. Menstrual blood has a similar pH-raising effect.
What Happens During Diagnosis
If you visit a healthcare provider, they’ll typically use a set of bedside criteria to diagnose BV. They’re looking for four things: the characteristic thin, gray-white discharge; a vaginal pH above 4.5; a fishy smell when a chemical solution is applied to a sample of the discharge (called a whiff test); and the presence of “clue cells” under a microscope, which are vaginal cells coated with bacteria. Meeting three of these four criteria confirms BV.
In some cases, a lab may also do a more detailed analysis using a scoring system that evaluates the ratio of healthy Lactobacillus bacteria to the types associated with BV. Scores of 0 to 3 indicate a healthy balance, 4 to 6 are intermediate, and 7 to 10 indicate bacterial vaginosis. This approach is considered the gold standard for research purposes, though the bedside criteria are what most clinicians use in practice.
Can You Test at Home?
Over-the-counter vaginal pH test strips are available at most pharmacies. They work by measuring whether your vaginal pH is elevated above 4.5. The FDA notes that these home tests show good agreement with a doctor’s assessment of pH. But there’s a significant catch: an elevated pH doesn’t confirm BV specifically. Trichomoniasis, certain STIs, menstrual blood, recent sex, and even non-infectious irritation can all raise vaginal pH.
A normal pH result doesn’t rule everything out either. You could still have a yeast infection, which doesn’t typically change pH, or another condition entirely. The home test is essentially one piece of a four-piece puzzle. It can tell you something is off, but it can’t tell you what. If your home pH test reads high and you’re also noticing thin, grayish discharge with a fishy odor, that combination is fairly suggestive of BV. But confirming the diagnosis and getting appropriate treatment still requires a provider visit.
Why BV Keeps Coming Back
BV is notorious for recurring. The bacterial imbalance resolves with treatment, but because the underlying environment can be easily disrupted again, many people experience repeat episodes. The same triggers apply each time: unprotected sex, douching, shifts in pH from menstruation or new partners. Some people are simply more vulnerable to these shifts than others for reasons that aren’t fully understood.
Reducing recurrence comes down to the same prevention steps that lower initial risk. Avoiding douching is the single most impactful habit change, since it strips away the protective Lactobacillus bacteria your vagina needs. Consistent condom use helps by preventing the pH disruption caused by semen. Limiting the number of sexual partners also lowers risk, though BV is not classified as a sexually transmitted infection in the traditional sense.