Clarithromycin
Tablet or syrup
Quick Summary
Clarithromycin is an alternative for people allergic to penicillin.
Medical Uses
How it's taken
Take it as prescribed, with or without food.
Take it for the full course, even if you feel better, unless your doctor tells you otherwise. Don't share antibiotics or keep leftovers.
Your doctor decides the right dose for you and how long to take it.
Your doctor decides the right dose for you. Follow their instructions and the label.
Common Side Effects
Altered taste
Common.
Diarrhoea
And nausea.
Headache
Sometimes.
Interactions
Statins
Simvastatin and some others can reach harmful levels.
Many other medicines
Tell your doctor about all your medicines.
Critical Warnings
Heart rhythm
Can affect heart rhythm.
Severe or bloody diarrhoea
Can be a sign of a serious bowel infection. Contact a doctor.
Severe allergic reaction
Black Box Warning: Swelling of the face or throat, difficulty breathing or a widespread rash: get emergency help.
Antibiotic resistance
Using antibiotics when they aren't needed makes them less effective for everyone.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Clarithromycin: drug information(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Clarithromycin: a medicine to treat bacterial infections(opens in a new tab) · NHS