How Many Probiotics Should I Take a Day for BV? Dose and CFU

One capsule a day, as the label says. The ten pooled trials behind the live-culture evidence for bacterial vaginosis (BV) gave 1.0 to 5.4 billion live cultures a day by mouth for 8 to 60 days of use, and when that 2022 meta-analysis of 1,234 women tested whether a bigger dose, a longer course or more strains gave a bigger effect, it found no link; there is no threshold count to clear.¹ The medicine for BV is a course of antibiotics from a GP or sexual health clinic. Live cultures were studied after that course, where the pooled trials found BV recurrence of 14.8% against 25.5%; nothing in those trials supports two capsules or a higher-count product.¹ This is the dose explainer in the Wellgard guide to what causes BV.

Sources checked on 29 October 2026.

How many probiotics should I take a day for BV?

The number on the pack. The trials behind the BV evidence did not hunt for a dose: each used the product as made and measured what happened weeks or months later. In the Nigerian trial of 125 women, an oral two-strain capsule, 1 billion of each twice a day, was taken for 30 days from the start of a week of metronidazole.² In the Vienna study of 72 postmenopausal women, the dose was 5 billion a day for 14 days.³ In the largest oral trial we found, 544 women in Croatia took the same two strains once a day for six weeks.⁴ Nobody took more because their BV was worse, and the pooled analysis found the daily dose unrelated to how far recurrence fell.¹ How do I take women's probiotics? covers timing, food and antibiotics; how long probiotics take to work for vaginal health covers the clock.

What does CFU mean, and which count matters on the label?

CFU stands for colony-forming units: the number of live bacteria in a dose that can each grow into a colony on a laboratory plate. Because it counts living cells, it falls over time: live cultures die slowly in the pack from heat, moisture and oxygen, and a 2019 review of how they are made describes the industry's answer, an overage at manufacture so the count still meets the label at the end of shelf life.⁵ A count "at time of manufacture" is the number on the day the capsules were made and says nothing about the day you swallow one; a count given for the end of shelf life is the live-culture count the label promises on its last day. The NHS adds that because live cultures are classed as food rather than medicine, it cannot always be sure a product contains the bacteria stated on its label.⁶ Compare the end-of-shelf-life count on the label, the named species and the storage instruction, and ignore a large number with no date attached; which count to look for on the label goes through the five checks.

Does a higher count work better?

Not on the evidence. The ten-trial analysis tested exactly this in a meta-regression and found dose, route, days of use and number of species all unrelated to the size of the recurrence effect.¹ The claim that an oral product needs 25 billion or more "to make it past the gut" has no trial behind it: the capsules in the BV trials carried 1 to 2.5 billion of each strain.^{2, 3} The count matters less than whether the strains have been studied for the outcome you care about, whether the count on the label is given for the end of shelf life, and whether you take it every day; how to choose between formats is a separate question.

Can taking too much probiotics cause BV, or can you overdose?

Taking too many live cultures does not cause BV. BV is the loss of the lactobacilli that normally dominate the vagina and hold its pH at around 3.5, and their replacement by a mixed growth of other bacteria; adding lactobacilli by mouth is the opposite direction of travel.⁷ The condition people sometimes have in mind is cytolytic vaginosis, where a woman's own lactobacilli are unusually abundant and itch, soreness and a thick white discharge mimic thrush while every swab comes back clear; a 2023 scoping review of 64 studies found no agreed diagnostic criteria and did not link it to supplements.⁸ As for overdose, the 2015 safety review ties the rare serious cases to who takes live cultures, not to how many; in healthy adults the side effects it describes are digestive and pass.⁹ Stay within the label dose because that is what the evidence describes.

Can probiotics alone do what antibiotics do?

No. Antibiotics are the treatment for BV: the NHS lists tablets, a gel or a cream prescribed by a GP or sexual health clinic.¹⁰ Live cultures were studied alongside or after that course. A 2022 meta-analysis found that adding live cultures to antibiotics raised the proportion of women whose BV had resolved by about a quarter (RR 1.23), while the three trials that set live cultures against antibiotics head to head were inconclusive.¹¹ A 2024 analysis of the largest vaginal trial found the recurrence benefit only in women whose antibiotics had worked first; where the course had failed, live cultures did nothing.¹² After oral antibiotics, BV returned in 58% of women within twelve months, which is why the after-antibiotics evidence matters: can I get rid of BV by taking probiotics? sets it out trial by trial, and why do I keep getting BV? covers the triggers.¹³

When does BV need a GP or a sexual health clinic?

If you think you have BV, the NHS says to see a GP or sexual health clinic (no referral needed), and that treatment matters in pregnancy; for more than four episodes a year a longer course of vaginal gel may be offered. Get help from NHS 111 if discharge changes colour, smell or texture, if there is more of it, if you are itchy or sore, if you bleed between periods or after sex, or if you have pain when peeing or pelvic pain.^{10, 15}

Who should take care with live cultures?

The serious cases in the safety review were almost all in people with a weakened immune system, a central venous line, a serious illness or recent major surgery, where live bacteria occasionally reached the bloodstream.⁹ Anyone in those groups, including anyone having chemotherapy or on medicines that suppress immunity, should review with a pharmacist or GP before starting. In pregnancy the trials found no safety problems and no benefit, including a UK trial of 304 women, so speak to a GP or midwife first.¹⁴

What we don't know

No trial has compared doses of live cultures for BV: each used one product at one dose, and the meta-regression that found no dose effect rested on ten trials, which its authors said was too few to be sure.¹ No oral trial for BV went above 5.4 billion a day, so higher counts are untested rather than disproved.¹ No study has linked the count on a UK label at the end of shelf life to any outcome in women. The only UK trial was in pregnancy and found no effect; there is none in non-pregnant UK women.¹⁴

Frequently asked questions

How much probiotic should a woman take daily?

The amount on the label, once a day. The oral trials behind the women's evidence gave 1.0 to 5.4 billion live cultures a day for 8 to 60 days, and the pooled analysis of ten trials found no link between the daily dose and the result, so a higher count has not been shown to do more.¹

Can you overdose on women's probiotic supplements?

The safety review ties the rare serious cases to who takes live cultures, not how many, and no trial has tested more than the label dose. One a day is the pattern the trials used.^{1, 9}

Is 1 billion CFU enough?

The ten pooled trials gave 1.0 to 5.4 billion a day by mouth and found no dose threshold, so 1 billion sits inside the range they tested.¹

How long should I take them after my antibiotics?

The ten pooled trials used live cultures for 8 to 60 days and counted recurrence at least one cycle after the antibiotics; review with a pharmacist or GP at about twelve weeks.¹

Sources

1. Chieng WK, et al. Probiotics, a promising therapy to reduce the recurrence of bacterial vaginosis in women? A systematic review and meta-analysis of randomized controlled trials. Frontiers in Nutrition, 2022. Meta-analysis, 10 RCTs, 1,234 women. PubMed 36204368.
2. Anukam K, et al. Augmentation of antimicrobial metronidazole therapy of bacterial vaginosis with an oral two-strain lactobacillus capsule: randomized, double-blind, placebo controlled trial. Microbes and Infection, 2006. RCT, 125 women. PubMed 16697231.
3. Petricevic L, et al. Randomized, double-blind, placebo-controlled study of oral lactobacilli to improve the vaginal flora of postmenopausal women. European Journal of Obstetrics & Gynecology and Reproductive Biology, 2008. RCT, 72 women. PubMed 18701205.
4. Vujic G, et al. Efficacy of orally applied probiotic capsules for bacterial vaginosis and other vaginal infections: a double-blind, randomized, placebo-controlled study. European Journal of Obstetrics & Gynecology and Reproductive Biology, 2013. RCT, 544 women. PubMed 23395559.
5. Fenster K, et al. The production and delivery of probiotics: a review of a practical approach. Microorganisms, 2019. Narrative review. PubMed 30884906.
6. NHS. Probiotics. Reviewed 24 November 2022. nhs.uk/tests-and-treatments/probiotics.
7. O'Hanlon DE, Moench TR, Cone RA. Vaginal pH and microbicidal lactic acid when lactobacilli dominate the microbiota. PLoS One, 2013. Observational study, 56 women. PubMed 24223212.
8. Kraut R, et al. Scoping review of cytolytic vaginosis literature. PLoS One, 2023. Scoping review, 64 studies. PubMed 36701339.
9. Doron S, Snydman DR. Risk and safety of probiotics. Clinical Infectious Diseases, 2015. Narrative review. PubMed 25922398.
10. NHS. Bacterial vaginosis. Reviewed 19 June 2026. nhs.uk/conditions/bacterial-vaginosis.
11. Chen R, et al. Probiotics are a good choice for the treatment of bacterial vaginosis: a meta-analysis of randomized controlled trial. Reproductive Health, 2022. Meta-analysis, 14 RCTs of live cultures added to antibiotics, 3 against antibiotics. PubMed 35698149.
12. Hemmerling A, et al. Response to antibiotic treatment of bacterial vaginosis predicts the effectiveness of a vaginal Lactobacillus crispatus live biotherapeutic in recurrent disease. Sexually Transmitted Diseases, 2024. Post-hoc analysis of a 228-woman RCT. PubMed 38733973.
13. Bradshaw CS, et al. High recurrence rates of bacterial vaginosis over the course of 12 months after oral metronidazole therapy and factors associated with recurrence. Journal of Infectious Diseases, 2006. Cohort study, 139 women. PubMed 16652274.
14. Husain S, et al. Effects of oral probiotic supplements on vaginal microbiota during pregnancy: a randomised, double-blind, placebo-controlled trial with microbiome analysis. BJOG, 2020. RCT, 304 pregnant women. PubMed 30932317.
15. NHS. Vaginal discharge. Reviewed 15 February 2024. nhs.uk/conditions/vaginal-discharge.

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General information, not medical advice. Food supplements are not a substitute for a varied and balanced diet and a healthy lifestyle; do not exceed the recommended daily dose.