Canestest has been clinically tested and is validated to detect changes in vaginal pH with more than 90% accuracy. This means that in clinical trials, the swab correctly identified whether vaginal pH was in the normal or elevated range — the primary biological marker used to distinguish BV from thrush — in over nine out of ten cases.

It is important to understand what the 90% accuracy refers to specifically. Canestest measures vaginal pH; it does not directly detect the presence of Gardnerella vaginalis, Candida albicans, Trichomonas vaginalis, or any other specific organism. The accuracy claim reflects the test's ability to detect a pH shift accurately — not its ability to provide a definitive laboratory-grade diagnosis. This means that Canestest should always be used in conjunction with your symptoms, using the symptoms table provided on the packaging, to arrive at the most reliable probable diagnosis.

The remaining margin means that in a small number of cases, the swab may indicate a normal pH even when BV is present (a false negative), or indicate an elevated pH even when no infection exists (a false positive — more likely in menopausal women, around the time of menstruation, or after sex). This is why the product guidance always states: do not make any decision of medical relevance without first consulting your medical practitioner, and always combine the result with your symptoms.

A blue or green swab result indicates that your vaginal pH is elevated above the normal acidic range (typically above 4.5). In the context of a woman of reproductive age who has no known factors that would independently raise pH, an elevated result combined with symptoms such as a fishy or unpleasant vaginal odour and a thin, grey or white watery discharge is strongly suggestive of bacterial vaginosis (BV). This is the most common explanation for an elevated vaginal pH result in a pre-menopausal woman without other complicating factors.

However, a blue or green swab result does not definitively confirm BV in isolation. Other considerations are important:

Trichomoniasis: If the blue/green result is accompanied by a frothy, yellow-green discharge, a strong or unpleasant odour, and painful or burning urination, trichomoniasis should be considered. Trichomoniasis is a sexually transmitted infection caused by the Trichomonas vaginalis parasite and also raises vaginal pH. If you suspect trichomoniasis, do not self-treat — consult your doctor promptly, as this condition requires specific prescription treatment and sexual partner notification.
Recent sexual intercourse: Semen is alkaline (pH typically 7.2–8.0) and can temporarily raise vaginal pH for several hours after sex. If you tested within 12 hours of intercourse, this may have contributed to or caused the elevated result. Wait at least 12 hours after sex before retesting.
Menstruation: Menstrual blood is alkaline and will raise vaginal pH significantly. Testing around the time of your period can produce a false elevated result.
Menopausal status: Post-menopausal women naturally have elevated vaginal pH due to declining oestrogen. A blue/green result in a menopausal woman does not reliably indicate BV.

If you receive a blue or green result and your symptoms are consistent with BV (fishy odour, thin watery discharge, no significant itching), the next step is to consult a pharmacist or doctor. BV requires prescription antibiotic treatment — either metronidazole tablets or Zidoval vaginal gel — and cannot be treated with over-the-counter products.

A yellow swab (no colour change) means your vaginal pH is in the normal acidic range (approximately 3.8–4.5). This is a reassuring result in terms of ruling out BV and trichomoniasis, because both of those infections raise vaginal pH. However, a yellow result has two possible interpretations depending on your symptoms:

Yellow swab + itching, soreness, and thick white cottage-cheese-like discharge with little or no odour: This combination is consistent with vaginal thrush (Candida albicans). Thrush is a yeast infection that does not significantly raise vaginal pH, so the swab remaining yellow is expected with a thrush infection. You can consider an appropriate over-the-counter antifungal treatment — for example Canesten Thrush Duo (clotrimazole pessary and cream) or a fluconazole 150 mg capsule. If you have had thrush before and recognise the symptoms clearly, treating with an OTC antifungal is reasonable. If this is your first suspected episode, or if you are unsure, consult a pharmacist or doctor.

Yellow swab + no significant symptoms: If the swab stays yellow and you have no significant symptoms — or only very mild, non-specific discomfort — it is possible that no significant common vaginal infection is present. It is worth considering whether there is another cause for any symptoms you are experiencing, such as skin irritation, an allergic reaction to a product, or another gynaecological condition.

A yellow result does not rule out all vaginal or sexual health conditions. In particular:

Canestest cannot detect sexually transmitted infections such as chlamydia, gonorrhoea, or herpes, which may not affect vaginal pH.
A yellow result does not rule out a mixed infection (for example, having both thrush and BV simultaneously — though this would typically raise pH and give a blue/green result).
If your symptoms are unusual, persistent, or do not resolve with appropriate treatment for thrush, seek a medical assessment.

For Canestest to give an accurate result, the vaginal pH reading must reflect your natural vaginal environment rather than temporary changes caused by external factors. Several common situations can independently alter vaginal pH and will produce an unreliable result:

During your period or within one day either side of it: Menstrual blood is alkaline and will raise vaginal pH significantly, almost certainly producing a blue/green (elevated pH) result regardless of whether BV is present. Do not use Canestest within one day before your period is due, during your period, or on the first day after your period ends.

Within 12 hours of sexual intercourse: Semen is alkaline (pH 7.2–8.0) and temporarily raises vaginal pH. Testing too soon after sex may give a false elevated result. Allow at least 12 hours to pass after intercourse before testing.

Within 12 hours of using a vaginal douche or vaginal product: Vaginal douches, gels, creams, and pessaries (including Canesbalance, Zidoval, Canesten pessaries, or similar products) can all temporarily affect vaginal pH. Wait at least 12 hours after using any such product. For pessary products in particular, Chemist4U pharmacy guidance notes that waiting 48 hours after using a vaginal pessary gives the most reliable result.

If any vaginal bleeding is present: Any vaginal bleeding — not just menstruation — will affect the pH reading. Do not test if you notice any unusual vaginal bleeding, and consult a doctor if unexpected bleeding is occurring.

Planning the timing of your test around these factors will significantly improve accuracy. If you are unable to wait — for example if you are in significant discomfort and want to start treatment — it may be more practical to consult a pharmacist or doctor directly rather than relying on a potentially affected test result.

• Do NOT test: If any vaginal bleeding is present
• Do NOT test: Within 12 hours of sexual intercourse
• Do NOT test: During your period or within 24 hours before or after
• Do NOT test: Within 12 hours of a vaginal douche or vaginal product use
• For pessary users: Wait 48 hours after using a vaginal pessary for best accuracy

Canestest is not suitable for all women, and its reliability is significantly affected by certain hormonal and life-stage factors that independently alter vaginal pH. Here is what you need to know for each group:

Menopausal and post-menopausal women — do not use: The menopause causes a significant and permanent decline in oestrogen levels. This leads to reduced glycogen in the vaginal epithelium, which in turn reduces the substrate available for lactobacilli to produce lactic acid. As a result, the vaginal pH of menopausal and post-menopausal women naturally rises above 4.5 — often reaching 5.0 to 7.0 — regardless of whether any infection is present. This means Canestest will almost certainly produce a blue/green (elevated) result in a menopausal woman even if she has no BV or trichomoniasis, making the test unreliable and potentially misleading. Menopausal women experiencing vaginal symptoms should consult their GP, pharmacist, or gynaecologist directly rather than using this test.

Pregnant women — consult your doctor first: If you are pregnant, you should not use Canestest to self-diagnose and self-treat without consulting a healthcare professional. Vaginal pH may be affected during pregnancy, and more importantly, selecting an appropriate treatment for any vaginal infection in pregnancy requires professional clinical guidance. Some treatments suitable for non-pregnant women are contraindicated or require specialist oversight during pregnancy, and certain infections (particularly BV) can carry increased risk of complications — including preterm labour — if not managed correctly. Consult your GP, midwife, or sexual health clinic if you are pregnant and experiencing vaginal symptoms.

Girls under 18 years of age — not intended for this age group: Canestest is intended for adult women only. Young people experiencing vaginal symptoms should see a healthcare professional for assessment.

Breastfeeding women: Breastfeeding reduces oestrogen levels, which can cause some women to have a slightly elevated vaginal pH. If you are breastfeeding and experience vaginal symptoms, it is advisable to consult your pharmacist or doctor rather than relying solely on Canestest, as the result may be influenced by your hormonal state.

⛔  Menopausal Women: Do Not Use Canestest

Menopausal and post-menopausal women will almost always receive a false blue/green (elevated pH) result due to natural hormonal changes — not because of BV or trichomoniasis. Using Canestest in this group risks an inaccurate and misleading diagnosis. Please consult a healthcare professional directly.