Sounds like 'kla-RITH-roe-MYE-sin'

Easy-to-read medicine information about clarithromycin – what it is, how to take it safely and possible side effects.

Type of medicine Also called
  • Antibiotic (to treat infections)
  • Macrolide antibiotic
  • Apo-Clarithromycin®
  • Klacid®
  • Clarac®

What is clarithromycin?

Clarithromycin is an antibiotic that is used to treat infections such as chest infections or skin infections. It works by killing or stopping the growth of bacteria (bugs) that cause infection. Clarithromycin is commonly used with other medicines to get rid of Helicobacter pylori, a bacteria that can cause stomach and duodenal ulcers. Read more about Helicobacter pylori


  • The usual dose of clarithromycin is 250 mg twice daily or 500 mg twice a day.
  • For children, the dose varies with age and weight.
  • Your doctor will advise you on how long to take clarithromycin for (usually 7 to 14 days).

How to take clarithromycin

  • Swallow the tablets with a glass of water.
  • You can take clarithromycin with or without food. 
  • Take your doses at the same times each day. 
  • Keep taking clarithromycin until you finish all the tablets. Do not stop taking it, even if you feel better after a few days.
  • If you forget to take clarithromycin, take it as soon as you remember. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.

Possible side effects

Abnormal heart rhythms

Clarithromycin can increase your risk of abnormal heart rhythms. It can cause fast, irregular heartbeats (known as arrhythmia), which may trigger a sudden fainting spell, or in some cases, if the heart does not regain its normal rhythm it may cause sudden death. You are at higher risk if you already have 'long QT syndrome', or if other members of your family have 'long QT syndrome'. You are also at increased risk if you have heart problems or are taking other medicines that cause 'long QT syndrome'. Read more about long QT syndrome

Other side effects

Like all medicines, clarithromycin can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Nausea (feeling sick) or vomiting
  • Take clarithromycin with or after food.
  • Diarrhoea (loose, watery stools)
  • Headache
  • These may go away with time.
  • Tell your doctor if troublesome.
  • Vaginal itching, soreness or discharge (thrush)
  • Tell your doctor or pharmacist.
  • Signs of problems with your liver such as yellowing of the skin or eyes, dark urine, pain in the abdomen. 
  • Tell your doctor immediately or ring HealthLine 0800 611 116 


  • Clarithromycin interacts with a few medicines and herbal supplements, so check with your doctor or pharmacist before starting clarithromycin.
  • Also, check with a pharmacist before taking over-the-counter medicines.

Learn more

The following links provide further information about clarithromycin. Be aware that websites from other countries may have information that differs from New Zealand recommendations. 

Clarithromycin for infection Patient Info, UK, 2016 


  1. Clarithromycin New Zealand Formulary
  2. Apo-clarithromycin Medsafe Datasheet, April 2015
  3. Macrolides - Don't Upset the Rhythm Medsafe Prescriber Update,  June 2015
Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 06 Sep 2017