Intravaginal Vitamin C: Promising Alternative in Treatment and Prevention of Bacterial Vaginosis

A recently published meta-analysis has systematically assessed the effectiveness of intravaginal vitamin C as a primary treatment and preventative strategy for bacterial vaginosis (BV) among nonpregnant patients. The analysis compared the use of vitamin C with both control and standard antibiotic therapy, providing a foundation for future high-quality clinical trials to further validate its use.

Understanding Bacterial Vaginosis

Bacterial vaginosis is the most common cause of abnormal, malodorous vaginal discharge in women of reproductive age, with a global prevalence estimated between 23% and 29%. BV is defined by a disruption in the normal vaginal microbiome, leading to an overgrowth of anaerobic bacteria and a reduction in protective Lactobacilli species. This imbalance can result in increased vaginal pH and is associated with an array of complications, including pelvic infections, heightened susceptibility to sexually transmitted infections, surgical site infections, and adverse pregnancy outcomes.

Current Diagnosis and Treatment Challenges

Diagnosis of BV typically relies on the Amsel criteria—requiring three out of four clinical signs such as homogeneous vaginal discharge, elevated vaginal pH, positive “whiff test,” and the presence of clue cells—or the Nugent score, a microscopic evaluation of vaginal fluid.

First-line treatment is usually broad-spectrum antibiotics, such as metronidazole or clindamycin. However, recurrence rates remain high, exceeding 50% within 6–12 months after treatment, prompting interest in alternative or adjunctive therapies, including probiotics, dietary modifications, microbiome transplants, and acidifying agents like vitamin C.

Meta-Analysis: Methods and Key Findings

The meta-analysis reviewed nine trials published up to May 2025, involving 1,107 participants. The studies assessed both short-term (1–2 weeks) and long-term (1 month) outcomes of vitamin C as either primary treatment or prevention of BV recurrence. Participants used 250-mg intravaginal vitamin C suppositories for six days per month, and all antibiotic controls involved metronidazole.

Key findings include:

Short-term Cure Rates: The vitamin C group demonstrated a higher proportion of short-term cure compared to controls (66% vs. 42%, RR 1.57) and compared to metronidazole specifically (62% vs. 52%, RR 1.20).

Resolution of Diagnostic Criteria: Vitamin C use resulted in greater resolution of certain Amsel criteria, notably the absence of clue cells and normalization of vaginal pH. Metronidazole, on the other hand, was more effective at reducing vaginal discharge.

Recurrence Prevention: At six months, BV recurrence was lower in the vitamin C group than in the placebo group (16% vs. 32%, RR 0.50). However, the difference at three months was not statistically significant.

Safety: Side effects such as vaginal irritation (18%), itchiness (8%), and burning (4%) were reported, but adverse events were uncommon and comparable between groups.

Implications and Limitations

While the certainty of evidence remains low due to the limited number of studies and lack of subgroup analysis or publication bias assessment, the results are promising. Intravaginal vitamin C appears to effectively acidify the vaginal environment, supporting Lactobacilli growth and inhibiting BV-associated anaerobes. Notably, vitamin C may outperform metronidazole in normalizing pH and eliminating clue cells, though metronidazole better reduces discharge.

Despite not being approved by regulatory agencies like the FDA, intravaginal vitamin C products (such as Prevegyne, Vagivit, and Vagi-C) are available over the counter in several countries, including in Europe and Canada.

Conclusion

Intravaginal vitamin C shows potential as an effective short-term treatment and preventative measure against BV recurrence. It may serve as a valuable adjuvant to antibiotics, though further high-quality studies are needed to bolster the certainty of these findings and assess the synergistic potential with standard therapies.

Key Takeaways

BV is the most common cause of abnormal vaginal discharge in reproductive-aged women, resulting from a disrupted vaginal microbiome and increased pH.

Standard treatment is broad-spectrum antibiotics, but recurrence is common.

Intravaginal vitamin C acts as an acidifying agent, promoting Lactobacilli growth and inhibiting anaerobes.

Vitamin C may be effective both as a stand-alone treatment and as an adjunct to antibiotics, with promising results in short-term cure rates and recurrence prevention.

More robust clinical trials are warranted to confirm these findings.

Reference:

Khaikin, Yannay et al. (2025). Intravaginal Vitamin C for the Treatment and Prevention of Bacterial Vaginosis: A Systematic Review and Meta-analysis. Obstetrics & Gynecology, 147. 10.1097/AOG.0000000000006092