The short answer
- White or off-white clumps, no itch or smell: most likely gel residue. Normal during and for a few days after treatment.
- Brown: usually old blood (light spotting, irritation from the applicator, or around a period).
- Thick white, itchy, burning: possibly thrush (yeast) after treatment. Grey, watery, fishy: BV may not have cleared or has come back.
How metronidazole gel works
Metronidazole vaginal gel 0.75% (MetroGel-Vaginal, Zidoval, and generic versions) treats bacterial vaginosis (BV), an imbalance where normal lactobacilli are replaced by other bacteria. The usual course is one applicator (about 5 g) inserted at bedtime for 5 days, or as prescribed. The gel spreads and slowly melts over the night, and some of it comes back out over the following days, often looking lumpy or crumbly when mixed with discharge.
What different discharge usually means
| What you see |
Likely cause |
What to do |
| White or clear clumps, gel-like, no smell |
Gel residue |
Normal; use a panty liner; finish the course |
| Brown or pinkish streaks |
Old blood from spotting, applicator irritation or period starting |
Usually harmless; see a doctor if bleeding is heavy, persistent or after menopause |
| Thick white “cottage cheese”, itch, burning |
Thrush (vaginal yeast infection) |
Pharmacy antifungal (clotrimazole, fluconazole) or see your GP |
| Grey-white, thin, fishy smell (stronger after sex) |
BV not cleared or recurred |
See your doctor; a different treatment may be needed |
| Yellow-green, frothy, or with pelvic pain or fever |
Possible sexually transmitted infection or pelvic infection |
See a doctor or sexual health clinic promptly |
Tips during treatment
- Insert the gel at bedtime and lie down, so less leaks out.
- Use panty liners, not tampons, during the course.
- Avoid vaginal sex, douching and perfumed washes during treatment; condoms and diaphragms may be weakened by some vaginal products, so check the leaflet.
- Avoid alcohol during treatment and for at least a day after, as the label advises (the effect is much less than with tablets, but caution is recommended).
- Finish the full course even if symptoms improve.
Why thrush can follow BV treatment
Antibiotics, including metronidazole gel, change the vaginal flora and can allow candida yeast to overgrow. Clinical trials of metronidazole gel report yeast infections in a minority of users. Typical symptoms are itch, soreness and thick white discharge. A pharmacist can recommend clotrimazole pessaries or cream or a single dose of oral fluconazole, unless you’re pregnant (see a doctor). If thrush keeps coming back, see your GP.
Other creams and gels, and when to see a doctor, are covered in the skin treatments guide.
When to see a doctor
See a doctor or sexual health clinic if symptoms haven’t improved by the end of treatment, if BV comes back (recurrence is common, and longer suppressive treatment may help), if you’re pregnant, if you have pelvic or abdominal pain, fever, bleeding after sex or after menopause, or if you might have been exposed to a sexually transmitted infection.
Frequently asked questions
Is green clumpy discharge after fluconazole normal?
Some clumpy discharge can continue for a few days as a yeast infection clears. Green or yellow discharge, especially with a smell or pain, is not typical of thrush and should be checked for other infections.
How long does gel discharge last after metronidazole?
Usually a few days after the last dose. If discharge persists beyond a week or changes in smell or colour, see a doctor.
Does my partner need treatment for BV?
Until recently, partners weren’t treated. A 2025 trial in the New England Journal of Medicine found that treating regular male partners at the same time (oral metronidazole plus clindamycin cream on the penis) roughly halved BV recurrence, and some services, particularly in Australia, now offer partner treatment. Ask your doctor or sexual health clinic what they recommend.
Sources and further reading
CanforaMedicine Guide
