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  1. About co-amoxiclav
  2. Key facts
  3. Who can and can't take co-amoxiclav
  4. How and when to take it
  5. Side effects
  6. How to cope with side effects
  7. Pregnancy and breastfeeding
  8. Cautions with other medicines
  9. Common questions

1. About co-amoxiclav

Co-amoxiclav is a combination antibiotic used for bacterial infections.

It contains amoxicillin (an antibiotic from the penicillin group of medicines) mixed with clavulanic acid. The clavulanic acid stops bacteria from breaking down amoxicillin, allowing the antibiotic to work better.

It is used in adults and children to treat:

The medicine is only available on prescription. It comes as tablets or as a liquid that you drink.

It's also given by injection, but this is usually only done in a hospital.

2. Key facts

  • For most infections, you'll start to feel better within a few days.
  • Usually you take co-amoxiclav 3 times a day.
  • The most common side effects of co-amoxiclav are diarrhoea, thrush and feeling or being sick.
  • Co-amoxiclav liquid can stain teeth. This is not permanent and brushing your teeth will remove any stains.
  • Co-amoxiclav is also called by the brand name Augmentin.

3. Who can and can't take co-amoxiclav

Co-amoxiclav can be taken by adults, including pregnant and breastfeeding women.

Co-amoxiclav can be taken by children.

Co-amoxiclav is not suitable for some people. To make sure co-amoxiclav is safe for you, tell your doctor if you:

  • have had an allergic reaction to amoxicillin, clavulanic acid, penicillin or any of the other ingredients
  • have had a severe allergic reaction to any other antibiotic. This can include a skin rash or swelling of the face and throat
  • have ever had liver problems or jaundice (yellowing of the skin) when taking antibiotics
  • have (or think you may have) glandular fever
  • have liver or kidney problems
  • are not peeing regularly


Co-amoxiclav liquid is not suitable for people with a rare inherited condition called phenylketonuria.

The liquid may contain aspartame, which may be harmful if you have this condition.

4. How and when to take it

The usual dose of co-amoxiclav is 1 tablet (either 375mg or 625mg) taken 3 times a day.

The dose may be lower for children. The doctor will use your child's weight to work out the right dose for them.

Try to space the doses out evenly throughout the day, at least 4 hours apart.


Carry on taking this medicine until you've completed the course, even if you feel better. If you stop your treatment early, the infection could come back.

How to take it

Take co-amoxiclav with a meal or snack. This will make you less likely to feel sick.

Swallow the tablets whole with a glass of water.

If you find tablets hard to swallow, you can break them in half. There is a line down the middle to make them easier to break. Take both pieces at the same time, swallowing one after the other.

If you are taking co-amoxiclav as a liquid, shake the bottle well before using. The medicine will come with a plastic syringe or spoon to help you measure out the right dose. If you do not have one, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not give the right amount.

What if I forget to take it?

If you forget to take a dose, take it as soon as you remember, then wait about 4 hours before taking your next one. However, if it's nearly time for your next dose just leave out the missed one and take your next dose as normal.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you forget doses often, it may help to set an alarm to remind you. You could ask your pharmacist for advice on other ways to remember your medicines.

What if I take too much?

Accidently taking 1 extra dose of co-amoxiclav is unlikely to harm you. Signs of taking too much co-amoxiclav might include an upset stomach (feeling or being sick, or diarrhoea) or having a fit (seizure).

Speak to your pharmacist or doctor as soon as possible if you take 2 extra doses or more.

5. Side effects

Like all medicines, co-amoxiclav can cause side effects, although not everyone gets them.

Common side effects

These common side effects happen in around 1 in 10 people. Keep taking the medicine but talk to your doctor or pharmacist if these side effects bother you or don't go away:

  • diarrhoea
  • itching, redness and discomfort in or around your mouth, armpits, vagina, penis or groin area – these are symptoms of thrush (a yeast infection)
  • feeling or being sick (nausea or vomiting), especially when taking high doses of co-amoxiclav

Serious side effects

Serious side effects are not common and happen in less than 1 in 100 people.

Tell a doctor straight away if you have:

  • a skin rash which may blister, and looks like small targets (central dark spots surrounded by a paler area, with a dark ring around the edge – these are signs of a skin reaction called erythema multiforme)
  • watery diarrhoea – usually with blood and mucus
  • stomach pain, possibly with a high temperature – these are signs of inflammation of the large intestines
  • pale poo with dark pee, yellowing of the skin or the whites of your eyes – these are warning signs of liver or gall bladder problems. This can happen even after you have finished taking this medicine

Immediate action required: Call 999 or go to A&E if:

  • you have had a seizure or fit (your body jerks and shakes)

Serious allergic reaction

In rare cases, co-amoxiclav can cause a serious allergic reaction (anaphylaxis).

Immediate action required: Call 999 or go to A&E if:

  • you get a skin rash that may include itchy, red, swollen or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of co-amoxiclav. For a full list see the leaflet inside your medicines packet.


You can report any suspected side effect to the UK safety scheme.

6. How to cope with side effects

What to do about:

  • diarrhoea – drink plenty of fluids, such as water or squash to avoid dehydration. Signs of dehydration include peeing less than usual or having strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor
  • thrush – ask your pharmacist or doctor for advice if this happens to you
  • feeling or being sick – stick to simple meals and do not eat rich or spicy food. Take co-amoxiclav with food. Drink lots of fluids, such as water or squash – take small, frequent sips if you feel sick to avoid dehydration. Signs of dehydration include peeing less than usual or having strong-smelling pee. Do not take any other medicines without speaking to a pharmacist or doctor

7. Pregnancy and breastfeeding

It's usually safe to take co-amoxiclav during pregnancy and while breastfeeding.

For more information about how co-amoxiclav can affect you and your baby during pregnancy, read this leaflet on the Best Use of Medicines in Pregnancy (BUMPS) website.


For safety, tell your doctor if you're trying to get pregnant, are already pregnant or if you're breastfeeding.

8. Cautions with other medicines

There are some medicines that do not mix well with co-amoxiclav.

Tell your doctor if you're taking these medicines before you start taking co-amoxiclav:

  • allopurinol or probenecid, which are used to treat gout
  • a blood thinner called warfarin
  • methotrexate, which is used to treat cancer or rheumatic diseases
  • mycophenolate mofetil, which is used to prevent the rejection of transplanted organs

Mixing co-amoxiclav with herbal remedies or supplements

There are no known problems with taking herbal remedies and supplements alongside co-amoxiclav.


For safety, tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.

9. Common questions

How does co-amoxiclav work?

Co-amoxiclav is a similar antibiotic to penicillin. It works by combining amoxicillin with clavulanic acid to kill the bacteria that cause an infection.

Sometimes amoxicillin cannot kill the bacteria on its own. This is because some types of bacteria produce an enzyme (called beta-lactamase) that breaks amoxicillin down.

Clavulanic acid prevents the enzyme from doing this, so that amoxicillin can work properly to kill the bacteria

When will I feel better?

For most infections, you should feel better within a few days.

It's very important that you keep taking co-amoxiclav until your course is finished. Do this even if you feel better. It will help stop the infection coming back.

How long will I take it for?

You will usually take co-amoxiclav for 5 to 14 days, depending on the type of infection.

If you do not feel better when you have completed your course of medicine, or if you feel worse at any time, talk to your doctor.

Is it safe to take for a long time?

You're generally recommended to take co-amoxiclav for up to 14 days.

Do not take this medicine for longer, unless the doctor has seen you again and thinks it is necessary.

What will happen if I stop taking it?

If you stop taking co-amoxiclav before your course of medicine has finished, the bacteria that are left will start multiplying again and the infection could come back.

The bacteria can also grow resistant to the antibiotic and this medicine might not work so well for you in the future.

If you do not feel better after finishing the medicine, or if you feel worse at any time, talk to your doctor.

Can I drink alcohol with it?

There's no specific warning about not drinking alcohol while taking co-amoxiclav.

However, if the medicine is making you feel sick, then drinking alcohol could make this side effect worse.

Drinking large amounts of alcohol while taking co-amoxiclav can make you more likely to get side effects affecting your liver.

Is there any food or drink I need to avoid?

Apart from not drinking too much alcohol, you can eat and drink normally while taking co-amoxiclav.

Will it affect my contraception?

Co-amoxiclav doesn't stop contraceptive pills working, including the combined pill or emergency contraception.

However, if co-amoxiclav makes you vomit or have severe diarrhoea for more than 24 hours, your contraceptive pills may not protect you from pregnancy.

Look on the pill packet to find out what to do. Read more about what to do if you're on the pill and you're being sick or have diarrhoea.

Will it affect my fertility?

There's no firm evidence to suggest that taking co-amoxiclav will reduce fertility in either men or women.

Can I drive or ride a bike?

Rarely, co-amoxiclav can cause side effects, such as dizziness, that could make you unfit to drive or cycle.

If this happens to you, do not drive a car, ride a bike, or use tools or machinery until you feel OK again.

Useful resources

Page last reviewed: 12 September 2019
Next review due: 12 September 2022