Like all medicines, co-amoxiclav can cause side effects, although not everyone gets them.
Common side effects
These common side effects of co-amoxiclav happen in up to 1 in 10 people. There are things you can do to help cope with them:
Diarrhoea
Drink plenty of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
If you take the combined contraceptive pill or progestogen-only pill and you have severe diarrhoea for more than 24 hours, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Thrush
Feeling or being sick (nausea or vomiting)
This can happen especially when taking high doses of co-amoxiclav.
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're being sick to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.
Do not take any other medicines without speaking to a pharmacist or doctor.
If you take the combined contraceptive pill or progestogen-only pill and you're being sick, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Keep taking the medicine, but speak to your doctor or pharmacist if the advice on how to cope does not help and a side effect is bothering you or does not go away.
Serious side effects
It happens rarely, but some people have a serious side effect from co-amoxiclav.
Call a doctor or call 111 now 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 whites of your eyes or your skin (this may be less obvious on brown or black skin) – these are 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 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Other side effects
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 using the Yellow Card safety scheme.