Amoxicillin is an antibiotic used to help treat bacterial infections in both adults and children.
It’s been available for decades, and is one of the most commonly prescribed of all medications: More than 50 million prescriptions for amoxicillin are filled in the United States each year.
When you start a new medication, it’s natural to wonder how long it will take to start working—so you’ll know when you’ll feel better.
In this article, I’ll tell you more about how amoxicillin works, and how fast it works.
I’ll also talk about when you should stop taking the antibiotic, the dangers of stopping too soon, and when to talk to your doctor or another healthcare professional.
What is Amoxicillin?
Amoxicillin is in the class of penicillin antibiotics.
It is broad-spectrum, meaning it works on lots of different bacteria.
Amoxicillin is made by pairing an extra amino group with penicillin, which helps combat resistance to the drug. It works by inhibiting bacteria’s ability to grow.
Sometimes secondary bacterial infections can occur after viral illnesses, and antibiotics may be needed.
Amoxicillin is often a first-line choice for this purpose.
If you are allergic to penicillin, you will likely be allergic to amoxicillin.
There are many different classes of antibiotics, and your doctor will make sure to choose one that is effective for your type of infection.
They will take your allergies, age, and other health-related factors into consideration when writing your antibiotic prescription.
Amoxicillin can be prescribed for many types of bacterial infections. Some common uses include:
- Dental infections such as periodontitis (gum disease)
- Ear, nose, and throat infections such a strep throat or bacterial sinusitis
- Bacterial pneumonia
- Urinary tract infections (often combined with clavulanic acid)
- Lyme disease
- Skin infections
- Anthrax exposure
- H. pylori infections (the bacteria that can trigger stomach ulcers)
Amoxicillin comes in a few forms.
Your doctor may prescribe it as a capsule, tablet, or a suspension (liquid).
Typically, people take amoxicillin twice to three times a day, or every 8-12 hours, either with or without food.
For adults, teenagers, and kids who weigh more than 88 pounds, the most common dose is 250-500 mg taken every eight hours, or 500-875 mg every 12 hours.
For children, doses range from 40-90 mg per kilogram of body weight, divided into 2-3 doses per day.
No matter how much you’re taking, aim to take your amoxicillin at the same time each day.
Your pharmacist or prescriber will give you dosing instructions and tell you exactly how to take your medication, including whether to take it with food.
Your medication should not be stored in a humid environment, like the bathroom.
Keep it in a cool, dry place out of sunlight.
Some medications may require refrigeration.
Ask your pharmacist if you have questions about how to take or store your medicine.
Infections that are not severe may be treated in as little as 3 days, but the typical course of treatment is 5-10 days.
Your prescription label insert will tell you how long you should take your amoxicillin.
If you forget to take a dose, do not panic.
If it has only been a few hours, take your dose and adjust your next ones accordingly.
If you are close to your next dose, skip your missed one and resume your schedule as normal. Never double up on amoxicillin doses.
Common Side Effects
Amoxicillin has some common side effects that are typical to many antibiotics. They may include:
More serious side effects can occur, though they are less common. If you notice any of these symptoms, discontinue your medicine and contact your doctor immediately.
- Itching, hives, or rash
- Wheezing or breathing problems
- Skin blisters
- Swelling of the lips, face, throat, tongue, or eyes
- Stomach cramps
- Severe diarrhea or bloody stools
This is not a complete list of possible side effects.
If you have questions or concerns while taking amoxicillin, ask your doctor or call your pharmacy.
How Fast Does Amoxicillin Work?
Amoxicillin starts addressing the bacteria that are causing your infection immediately, but you will not feel better immediately.
Amoxicillin will typically help you to start feeling better within a few days.
However, it may take up to 4-5 days before your symptoms improve.
When to Stop Taking Amoxicillin
Do not stop taking amoxicillin unless your prescription runs out or your doctor tells you to stop.
Even if you are feeling better, the medication still needs to finish addressing the bacterial infection.
Stopping early could lead to a resurgence of bacterial growth and could make them resistant to the next course of antibiotics.
If there is any amoxicillin leftover when you are done taking it, discard it.
Do not flush it down the toilet and do not save it.
It is considered to be expired and unsafe for use after 14 days.
Antibiotics should always only be taken for the specific purpose they were prescribed for.
Bacteria have the ability to adapt to their environment.
Because of this, when they are threatened by antibiotics, they may be able to adapt and avoid being destroyed the next time they are exposed.
Much like viruses can mutate, bacteria can also evolve.
When bacteria evolve so that an antibiotic doesn’t work as well, the bacteria is considered “drug-resistant,” or antibiotic resistant.
Antibiotic resistance is a global health problem.
Millions of people are infected with drug-resistant bacteria each year.
In some cases, infections can be fatal.
The people primarily at risk of these superbugs are those who have a chronic illness or weakened immune systems, but everyone is technically impacted by potential risks.
You can reduce your risk of drug-resistant infections by only taking antibiotics when they are absolutely necessary and by taking them exactly as prescribed.
When to See a Doctor
You should see a doctor if you have been sick with a cold or flu but don’t seem to be improving after 7-10 days.
If your fever gets worse or other symptoms concern you, check in with a health care provider.
They may want to do some tests to determine if your illness is caused by a virus or bacteria. If a bacteria is causing your problem, you may not get better unless antibiotics are given to treat the infection.
How K Health Can Help
You can speak with primary care providers through K Health, without having to leave your home. Get peace of mind about your symptoms and, if needed, get a prescription.
Download the K app to check your symptoms, explore conditions and treatments, and if needed text with a doctor in minutes. K Health’s AI-powered app is HIPAA compliant and based on 20 years of clinical data.
Frequently Asked Questions
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.
K Health has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.
Three day versus five day treatment with amoxicillin for non-severe pneumonia in young children: a multicentre randomised controlled trial. (2004).
Using medication: Using antibiotics correctly and avoiding resistance. (2013).
About antibiotic resistance. (2020).
Antimicrobial resistance. (2021).