What Is Vaginal pH, What Should It Be and How Is It Measured?

In brief:

• Vaginal pH is usually between 3.8 and 4.5; it may be higher before a period and after menopause (Cleveland Clinic).
• Menstrual blood, semen, douching, scented products and antibiotics can affect pH (Cleveland Clinic).
• A pH above 4.5 is one of the four diagnostic criteria for bacterial vaginosis; in vaginal thrush, pH is usually normal (CDC).
• A home pH test can show whether pH is off balance, but it cannot tell you why (Cleveland Clinic).

What is vaginal pH?

pH is a scale from 0 to 14 that shows how acidic or alkaline something is; 7 is neutral and below 7 is acidic. In a healthy vagina, pH is usually between 3.8 and 4.5 (Cleveland Clinic).

This mild acidity is a defence system: it helps beneficial bacteria in the vagina grow and makes it harder for harmful germs to settle (Cleveland Clinic). We explain the inside of the vagina and how it differs from the outer area in A Guide to Intimate Area Care.

What should vaginal pH be?

• 3.8–4.5: Normal range (Cleveland Clinic).
• Above 4.5: Can be normal just before a period starts and after menopause (Cleveland Clinic). Otherwise, it is one of the findings seen in bacterial vaginosis (CDC).

Because hormone levels change after menopause, a pH above 4.5 is not considered a sign of infection on its own.

What changes vaginal pH?

According to Cleveland Clinic:

• Menstrual cycle and hormones: pH changes through the cycle, in pregnancy and in menopause. Birth control pills can also affect it.
• Sex: Semen, lubricants and condoms can affect pH.
• Douching and harsh products: Washing inside the vagina, and products with irritating chemicals or perfume, can upset pH.
• Antibiotics: They can kill beneficial bacteria as well as harmful ones.
• Infections: Bacterial vaginosis, vaginal thrush and trichomoniasis affect pH.

What symptoms occur when pH is off balance?

When pH balance is upset, you may notice (Cleveland Clinic):

• A fishy or bad vaginal smell
• Grey, green, frothy or clumpy discharge
• Itching, swelling or irritation of the vulva
• Pain or burning during sex or when peeing

These symptoms can occur in different conditions. We explain what discharge colours may mean in When Is Vaginal Discharge Normal?.

Vaginal pH and infections

pH is a clue, not a diagnosis:

• Bacterial vaginosis: One of the four criteria the CDC uses for diagnosis is a vaginal fluid pH above 4.5. The other criteria are thin, uniform discharge, a positive odour test and typical cells seen under a microscope. At least three must be present together for a diagnosis. Details are in What Is Bacterial Vaginosis?.
• Vaginal thrush: According to the CDC, vaginal pH is usually normal (below 4.5) in a yeast infection. So a normal pH does not rule out thrush. We explain the symptoms and when to see a doctor in What Is Vaginal Thrush?.

How is vaginal pH measured?

During an examination, a doctor can measure vaginal discharge with pH paper. This is one of the criteria used for bacterial vaginosis (CDC).

Home vaginal pH tests also work with a colour-changing paper: the paper is touched against the vagina, and when its colour changes it is compared with the colour chart on the box (Cleveland Clinic). These tests can give an idea of whether pH is off balance, but they cannot tell you why and do not show which infection it is (Cleveland Clinic).

If you do the test, follow the instructions on the box. Because menstrual blood and semen can affect pH (Cleveland Clinic), a measurement taken during a period or straight after sex may be misleading.

How do you keep vaginal pH in balance?

The vagina cleans itself; there is no need to wash inside it. The NHS recommends:

• Wash the vulva with water and plain soap; take showers rather than baths.
• Do not wash inside the vagina or douche.
• Do not use scented soaps, bath products or vaginal deodorants.
• Do not wash your underwear in harsh detergent.
• Do not smoke.

Cleveland Clinic also recommends avoiding scented sprays, soaps, pads and tampons, and changing out of wet or sweaty clothes promptly. We have gathered the other rules of genital hygiene in The Basic Rules of Genital Hygiene.

When should you see a doctor?

• If symptoms such as smell, discharge or itching last longer than a few days, get worse or do not go away (Cleveland Clinic)
• If a home test showed high pH and you have symptoms
• If you are pregnant and notice a change in discharge or smell
• If symptoms keep coming back

Treatment depends on the cause; antibiotics or antifungal medicine may be needed (Cleveland Clinic). See a doctor rather than diagnosing yourself.

Frequently asked

What should vaginal pH be?

Usually between 3.8 and 4.5 (Cleveland Clinic). It may be slightly higher before a period and after menopause.

Can you buy a vaginal pH test at a pharmacy?

Home vaginal pH tests are sold in some pharmacies. These tests can show whether pH is high, but they cannot tell you why (Cleveland Clinic). Whatever the result, see a doctor if you have symptoms.

Why does vaginal pH rise in menopause?

In menopause, hormone levels change and vaginal pH can rise above 4.5; this can be normal after menopause (Cleveland Clinic). We explain how menopause affects the intimate area in Why Do Intimate Care Needs Change During Menopause?.

Does soap upset vaginal pH?

Using soap or shower gel inside the vagina, douching and scented products can upset pH (Cleveland Clinic). The outer area is washed with water and plain soap (NHS).