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How Long Does Amoxicillin Take to Work?

Amoxicillin fights infections in the body within an hour after taking it. The penicillin-based medication gets its strength from consistent use of multiple doses per day. Amoxicillin often relieves symptoms in less than 72 hours and stays in your system for 24 hours.

Last Modified: September 5, 2023
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How Quickly Does Amoxicillin Work?

Amoxicillin is a fast-acting antibiotic that begins working almost immediately after someone takes a dose, and it reaches full effectiveness about an hour or two later.

However, taking amoxicillin does not relieve symptoms of infection immediately. It takes most people around 72 hours to feel better when taking antibiotics, though some people notice improvements sooner within one or two days (24-48 hours).

A person’s antibiotic resistance may also cause amoxicillin to take longer to work. This occurs when bacteria adapt their biology enough to avoid being killed by the antibiotic.

Taking antibiotics frequently may lead to the bacteria in your body developing more resistance to the medications. Always let your doctor know if your antibiotics do not seem to work as intended.

Some Foods May Impact Amoxicillin’s Absorption

Some medical evidence shows that certain foods and drinks may slow down amoxicillin’s effects. According to some studies, green tea interferes with the absorption of antibiotics.

Caffeine is generally considered safe to consume while taking amoxicillin. However, the relationship between green tea, which is highly caffeinated, and amoxicillin is still under investigation because of caffeine’s potential effect on gut bacteria. Researchers say they need data from more studies to determine if and how much caffeine may interfere with amoxicillin absorption.

Unlike some medications, amoxicillin does not come with label warnings to avoid alcohol when taking the medication. Multiple studies show that drinking alcoholic beverages slows down the rate at which the body absorbs the drug but does not affect the overall extent of its absorption.

How Long Will Amoxicillin Work After Taking It?

Amoxicillin works the entire time it’s in your body. The maximum safe dose of amoxicillin is 4,000 mg per day, according to the drug’s label, but few people need to take that much.

Dosing schedules keep amoxicillin in your system continuously, making the drug work more effectively to fight your infection.  The University of California San Francisco recommends the following dosage limits:

  • Suspension: 1,000 mg per dose twice a day (2000 mg in total)
  • Tablets: 1,000 mg per dose (two 500 mg tablets) taken twice a day
  • Amoxicillin-clavulanate (Augmentin) tablets: 2,000 mg (two 1,000 mg tablets) per dose, twice a day, if you have acute bacterial sinusitis with systemic illness, a high fever or a compromised immune system

While amoxicillin does work the entire time it’s in your system, it becomes less effective after the first few hours. This is why doctors prescribe it in multiple daily doses and not one larger dose per day. Spacing out doses gives your body a fresh supply of amoxicillin every few hours, allowing you to fight an infection around the clock.

Doctors may prescribe more frequent doses of amoxicillin if they feel you would benefit from more consistent support while you heal. For instance, doctors usually treat a lower respiratory tract infection with 875 mg of amoxicillin taken twice a day. However, doctors sometimes prescribe 500 mg of amoxicillin taken three times a day to keep the drug at more consistent levels in your body.

How Long Does Amoxicillin Stay in Your System?

Amoxicillin stays in your system for 24 hours. But the estimate depends on the dosage. The amount of amoxicillin taken at one time impacts its half-life.

A drug’s half-life is the time it takes for only half of the drug to be present in your blood after your last dose. Amoxicillin’s half-life is around one hour.

Six hours after taking amoxicillin, less than 2% of the drug will still be in your system. Your body will process the last traces of the drug for the rest of the day.

Larger doses of amoxicillin (ones greater than 500 mg in capsule or tablet form or 5.5 mcg/mL in suspension form) get processed more slowly. Such dosages have a half-life of two hours and will take about 12 hours to reach the same 2% marker. The medication remains in your system about twice as long as lower doses.

When to Stop Taking Amoxicillin

One of the chief labeling guidelines of amoxicillin is to finish the prescription. Doctors reinforce this. Do not stop taking amoxicillin until your doctor says it is OK or until you run out of your prescription.

Findings from one 2022 clinical research trial suggested that a short course of Amoxicillin (5 days) was just as effective as a longer course (10 days) for uncomplicated commonly acquired pneumonia in children under 10 years old.

Antibiotics like amoxicillin need time to clear bacteria out of your body. Most people feel better long before amoxicillin eradicates all of the bad bacteria, leading them to believe that they are cured. This is not true.

If infectious bacteria remain in your body and you stop short of finishing your prescription of amoxicillin, you could suffer a relapse of your infection. Taking your medication exactly as prescribed prevents this from happening. If you have questions about amoxicillin, instructions for your specific prescription, or how amoxicillin interacts with other medication speak, with your doctor.

Please seek the advice of a medical professional before making health care decisions.