How long it takes antibiotics to work depends on the antibiotic prescribed and how severe the infection is. In general, antibiotics start working within a few hours, but noticeable improvement usually happens within 48 to 72 hours after starting treatment.
If symptoms do not improve as expected, it may be because the infection is not caused by bacteria, the antibiotic is not the most appropriate choice, or the dose is too low. Missing doses, interactions with food or other medicines, and antibiotic resistance can also reduce how well the treatment works.
If you notice little or no improvement after the first few days of antibiotics, or if symptoms get worse, you should follow up with the healthcare provider who prescribed the treatment. A primary care provider or an infectious disease specialist can reassess your symptoms and adjust treatment if needed.
Antibiotics are used to treat bacterial infections by stopping bacteria from multiplying or helping the body eliminate them. Using antibiotics incorrectly can lead to antibiotic resistance, which can make future infections more difficult to treat. Even if symptoms improve, the full course should be completed as directed by a healthcare provider.