How long does it take metronidazole to work?

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Overview

Metronidazole (Flagyl) is a generic antibiotic drug that doctors use to treat infections caused by bacteria or parasites, such as:

• sexually transmitted diseases and infections (STD and STIs) like trichomoniasis
• certain gastrointestinal infections
• certain respiratory tract infections
• skin and soft tissue infections
• bone and joint infections

Metronidazole comes in multiple forms, which include:

• capsule or tablet (that you take by mouth)
• a gel (that you apply to your skin)
• an injection (that a healthcare professional gives)

You will need a prescription from your doctor to get metronidazole. It is not available over the counter (OTC).

How long does it take metronidazole to clear up a bacterial infection?

Metronidazole starts working a few hours after you take your first dose. But it may take a few days before you start to feel better or notice relief from your symptoms. Most infections will clear up after about 5 to 10 days of taking metronidazole. Hwoever, it may take longer for most serious infections, like bone, heart, and respiratory tract infections.

Metronidazole will clear up certain bacterial infections depending on the type of infection. The following list includes the time it takes to clear the infection:

• Trichomoniasis: The doctor may prescribe a single dose of metronidazole or a longer course of 5 to 7 days. Metronidazole should clear up your infection in about a week.
• Bacterial vaginosis: Doctors may prescribe oral metronidazole or topical metronidazole for bacterial vaginosis (BV). It will typically take about 5 to 7 days for metronidazole to clear up a BV infection.
• Skin conditions like rosacea: Your dermatologist or doctor will typically prescribe the topical form of metronidazole for rosacea. It may take 3 to 4 weeks to notice the desired results.
• Parasitic infections of the intestines: Doctors may prescribe metronidazole to help clear up infections like giardiasis or amebiasis, which parasites cause in your intestines and often cause diarrhea. It typically takes about 7 to 10 days to clear up amebiasis and 5 to 7 days to clear up giardiasis.
• Bacterial infection in the bones or joints: Infections in the bones and joints can be more difficult to treat and require longer treatment courses. It could take about 2 weeks to see symptom relief, and it may take up to 4 to 6 weeks to clear up these infections.
• Respiratory tract infections: Bacterial infections of the respiratory tract can be more difficult to treat and require longer treatment courses. It could take about 2 weeks to see symptom relief, and it may take up to 4 to 6 weeks to clear up these infections.

It’s important that you take metronidazole for the full course of time it’s been prescribed to you. Even if your symptoms improve and you start to feel better, it doesn’t mean your infection has fully cleared up. Stopping metronidazole treatment early may result in your infection returning. It’s also possible that some bacteria may survive and become resistant to antibiotics, making infections harder to treat in the future.

How do I know if metronidazole is working?

You can tell metronidazole is working when you start to notice relief from the symptoms of your bacterial infection.

These symptoms will vary depending on what ype of infection you have. For example, you may have less diarrhea when metronidazole is working to treat intestine infections like giardia. With infections like BV, you’ll know metronidazole is working when you notice less unusual vaginal discharge and the discomfort and fishy odor go away.

If you don’t notice any symptoms resolving or if you still don’t feel better 2 to 3 days after finishing your course of metronidazole, talk with your doctor. Also, let them know if you start to feel worse or experience side effects that don’t go away.

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Summary

Although metronidazole starts to work as soon as you start taking it, it typically takes 5 to 10 days to clear up an infection. It may take longer if you are using a topical form of metronidazole or taking it for a more serious infection in the bones, joints, heart, or respiratory tract.

You’ll know metronidazole is working when you notice relief in your symptoms and the infection starts to clear up.

It’s very important that you take metronidazole exactly as your doctor prescribes. You should finish your full course of the drug, even if you start to feel better early. Finishing your full course of metronidazole will help stop the infection from returning.