The prescription medicine metronidazole should start to work within 2 to 3 days of taking it.
If you do not notice any improvements in your symptoms or you do not feel better within 3 to 4 days of taking the metronidazole you should let your doctor know about it.
Your dosage may need to be increased.
However do not increase your own dosage of metronidazole without a doctors approval because you could overdose if you take too much.
Most people however do see improvements and feel better within 3 days of taking the metronidazole.
The metronidazole does not work overnight but overtime it does work good.