What is Amoxicillin: Dosage, Side Effects, and More

By Arielle Mitton
Medically reviewed checkmarkMedically reviewed
December 23, 2021

Amoxicillin is a common antibiotic used to treat bacterial infections.

It is in a class known as penicillin-like antibiotics and can be safely used in both adults and children.

If it’s prescribed to you by your healthcare provider. It is important to know the potential side effects and how to safely take it.

Amoxicillin Basics

Amoxicillin, like many other kinds of antibiotics, is broad-spectrum and works by preventing bacterial growth.

It pairs an amino with penicillin, making it penicillin-like.

This is done to help make the medication more effective against certain types of bacteria and to decrease the possibility of antibiotic resistance.

It is effective against bacteria because it destroys its ability to make a protective cellular exterior, which allows them to be destroyed.

However, bacteria can adapt to their environment, and when they get exposed to an antibiotic enough times, they may be able to adapt to prevent being destroyed.

This is what is known as becoming drug-resistant.

Amoxicillin does not work for viral infections like the cold or flu, but it may be used to treat bacterial infections that occur after a virus.

If you are prescribed amoxicillin, you will probably start to feel better within a few days.

However, you should finish your prescription unless your doctor tells you to stop.

Bacterial infections can improve on antibiotics, but it still takes time for the replication of bacteria to be stopped.

If you discontinue your antibiotic too soon, your infection could come back and be resistant to that antibiotic next time.

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What is Amoxicillin Used For?

Amoxicillin is used to treat bacterial infections. These may include:

Amoxicillin may be paired with clavulanic acid which can help to keep bacteria from destroying the amoxicillin.

What Are the Side Effects of Amoxicillin?

Like many antibiotics, amoxicillin can cause some common side effects.

Most of them tend to be mild. If they are severe, get worse, or are concerning, speak to your doctor immediately.

In rarer cases, serious side effects can occur.

If you have any of the following symptoms, discontinue your medication and contact your doctor right away or seek emergency medical help.

  • Itching, hives, or rash
  • Skin blisters
  • Wheezing or difficulty breathing
  • Difficulty swallowing
  • Swelling of the face, lips, throat, tongue, or eyes
  • Severe diarrhea and/or bloody stools
  • Stomach cramps

Other side effects are possible.

If you have questions or concerns while taking amoxicillin, talk to your doctor or pharmacist.

What to Know Before Taking Amoxicillin

Amoxicillin is not safe for everyone.

Before taking amoxicillin, you should be sure that your doctor and pharmacist gets your health history and knows the other medications that you are taking.


Patients who are allergic to amoxicillin and similar medications, like penicillin antibiotics, cephalosporin, cephalexin, and others should not take amoxicillin.

Medical advice typically suggests avoiding alcohol during antibiotics.

Even though alcohol and amoxicillin don’t directly interact, alcohol intake can change the way that your medication is absorbed.

Alcohol may also affect how well your immune system functions, which is problematic when you are already fighting an infection.

Make sure that your doctor knows if you have mononucleosis, kidney disease, liver problems, asthma, hives, hay fever, or other allergies.

These may change the prescription or dosage that your doctor recommends.

Amoxicillin can be damaging to your kidneys and liver if you have existing problems because the liver metabolizes the drug, and the kidneys remove it from the body.

If you have phenylketonuria (PKU), avoid the chewable tablets since they contain aspartame, which forms phenylalanine.

Since amoxicillin is mainly cleared from the body via the kidneys, having renal insufficiency or other kidney disorders may require that your doctor recommend a different medicine.

Amoxicillin may cause discoloration in children’s teeth, so it should be used with caution and not too frequently.

Tell your doctor or pharmacist if your child has recently or ever taken amoxicillin.

If you have to get urine glucose tests for diabetes, you should be aware that amoxicillin may interact with the accuracy of these test results.

Tell your health care provider that you are taking amoxicillin if you need to get a urine glucose test.

Pregnancy and Breastfeeding

Amoxicillin should not be taken during pregnancy or breastfeeding.

If you get pregnant while you are taking amoxicillin, inform your doctor right away.


Penicillin allergies are somewhat common, and people who are allergic to penicillin may also react to amoxicillin.

You can also have an allergic reaction to inactive ingredients in the drug, so be sure to read drug labels and ask your pharmacy questions.

Drug Interactions with Amoxicillin

If you take other prescription medications, OTC drugs, dietary supplements, or herbs, be sure that your doctor and pharmacist know.

The following have known interactions with amoxicillin, but others may occur that are not listed here:

  • Allopurinol
  • Other antibiotics
  • Blood thinners
  • Oral contraceptives
  • Probenecid

These are not the only drugs that may cause adverse effects.

It’s important to tell your doctor everything that you take to prevent problems.

How To Take Amoxicillin

Your prescription label insert will provide information about how long you will be taking amoxicillin.

Be sure to take it at consistent intervals.

If you forget to take a dose, do not double up. Take your next regularly scheduled dose at the normal time, or take it as soon as you remember.

Then take your next dose 8 or 12 hours later, at whatever interval you were prescribed.

Do not store your medication in the bathroom; the fluctuating heat and humidity levels from showering may have a negative effect.

Keep it in a cool, dry place out of the reach of children and out of direct sunlight.


Amoxicillin comes in tablets, chewable tablets, capsules, and a liquid suspension.

It is often dosed to be taken every 12 hours or every 8 hours.

Amoxicillin may be taken with or without food.

If you or your child are taking amoxicillin in suspension form, be sure to close the lid tightly and shake completely before measuring a dose.


Dosage for amoxicillin medication for adults can range from 750-1750 mg per day, divided between 2-3 doses.

In children, the dosage is 20-45 mg per kilogram of body weight per day, divided between 2-3 doses.

Your pharmacy will provide you with clear dosage instructions.

If you are unsure about any part of your medication regimen, ask your doctor or pharmacist.

Your doctor will prescribe the shortest course of antibiotics that will be effective.

Non-severe infections may be effectively treated in as little as 3 days.

When to Stop Taking

Take your full course of amoxicillin and don’t stop unless your doctor tells you otherwise.

If you stop antibiotics before they have eliminated the bacterial infection, it can contribute to antibiotic resistance.

If you have leftover medication when your doctor says it is okay to stop, dispose of it.

Do not flush it down the toilet, and do not save it.

Amoxicillin is considered expired and ineffective after 14 days.

You should never take antibiotics unless they have been prescribed for a specific purpose.

Alternatives to Amoxicillin

If you are allergic to amoxicillin or cannot take it for another reason, there are some commonly used alternatives. These include:

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When to See a Doctor

If you are sick but suspect that you have a viral infection, you should see your doctor if you fail to improve as expected, especially if a fever is still present. 

If you are taking amoxicillin and are worried about any symptoms or side effects, speak with your doctor to get your questions answered.

How K Health Can Help

If you are sick or don’t want to leave the house to get your antibiotic questions answered, you can work with a primary care provider right from the comfort of your home.

Download K Health to check your symptoms, explore conditions and treatments, and if needed text with a provider in minutes. K Health’s AI-powered app is based on 20 years of clinical data.

Frequently Asked Questions

Are there special dietary restrictions to follow when taking amoxicillin?
There are no specific dietary restrictions or changes required when taking amoxicillin. Most doctors will recommend avoiding alcohol since it can decrease your immune system’s response and may adjust how your body absorbs the medication.
What happens if I miss a dose of amoxicillin?
If you miss a dose, do not double up. Take your dose as soon as you normally would. If you are closer to when your next dose would be due, skip the missed dose and resume your normal schedule.
When will amoxicillin start working?
Most antibiotics start helping you feel better from infection symptoms within a few days. Depending on the type of illness or infection you have, it may take 4-5 days to notice improvements. Even when you feel completely better, you should still finish your entire prescription. This will help to decrease the chance of recurring infections or antibiotic resistance.
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.

Arielle Mitton

Dr. Mitton is a board certified internal medicine physician with over 6 years of experience in urgent care and additional training in geriatric medicine. She completed her trainings at Mount Sinai Hospital and UCLA. She is on the board of the Hyperemesis Research Foundation to help women suffering from hyperemesis gravidarum.

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