Cefalexin is an antibiotic used to treat different infections caused by bacteria. Find out how to take it safely and possible side effects.

Type of medicine Also called
  • Antibiotic (to treat infections)
  • Cefalexin (Sandoz)®
  • Cefalexin ABM®

What is cefalexin?

Cefalexin is an antibiotic used to treat infections caused by bacteria, such as infections of the urinary tract, skin or chest. It can also be used for dental infections or ear infections. It works by killing or stopping the growth of bacteria (bugs) and gets rid of the infection. Cefalexin does not work against infections caused by viruses. In New Zealand cefalexin is available as capsules and liquid.


  • The dose of cefalexin will be different for different people depending on the type of infection and your age. 
  • Adults: the usual dose is 250 mg four times a day, or 500 mg two, three or four times a day. Some people may need a larger dose. 
  • Children: the dose for children will depend on their body weight. It may be given two, three or four times a day.
  • Your doctor will advise you how long to take cefalexin for (usually 5 to 7 days).
  • Always take your cefalexin exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much cefalexin to take, how often to take it, and any special instructions.

 How to take cefalexin

  • You can take cefalexin with or without food.
  • Capsules: swallow your capsule with a glass of water. Do not chew them.
  • Liquid: shake the medicine well. Measure the right amount using an oral syringe or medicine spoon. You can get these from your pharmacy. Do not use a kitchen spoon as it will not give you the right amount. Read more: tips on how to give medicines to babies and children.
  • Timing: Try to space your doses evenly throughout the day.  
    • Two times a day: this should be in the morning and in the evening. 
    • Three times each day: this should be in the morning, early afternoon and at bedtime. 
    • Four times each day: this should be about 4 hours apart, for example 7am, 11am, 3pm and 7pm.  
  • Missed dose: If you forget to take your dose at the correct time, take one as soon as you remember. Try to take the correct number of doses each day. Do not take two doses at the same time to make up for a forgotten dose.
  • If you are sick: If you are sick (vomit) less than 30 minutes after having a dose of cefalexin, take the same dose again. But, if you are sick (vomit) and it is more than 30 minutes after having a dose of cefalexin, you do not need to take another dose. Wait until the next normal dose.  
  • Finish the course. It is best to take the whole course of antibiotics for the number of days your doctor has told you to. Do not stop taking it, even if you feel your infection has cleared up. 
  • Alcohol: You can drink alcohol while taking cefalexin.

Precautions when taking cefalexin

Before starting cefalexin

  • Have you ever had an allergic reaction to a medicine, especially a penicillin antibiotic?
  • Do you suffer from collitis or severe diarrhoea?
  • Do you have problems with your kidneys?
  • Are taking any other medicines? This includes any medicines you are taking which you can buy without a prescription, as well as herbal and complementary medicines.

If so, it’s important that you tell your doctor or pharmacist before you start cefalexin. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

While taking cefalexin

Store your capsules in a cool, dry place, away from direct heat and light. If you have been given liquid medicine, this will have been made up by the pharmacy and you may need to keep it in the fridge - check the instructions on the bottle. Make sure the medicine does not freeze.

What are the side effects of cefalexin?

Like all medicines, cefalexin 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?
  • Feeling sick (nausea) or vomiting
  • Dizziness, headache
  • Try taking cefalexin with food.
  • Tell your doctor if troublesome.
  • If you have been vomiting and are also taking the oral contraceptive pill, let your doctor or pharmacist know.
  • Diarrhoea (runny poos)
  • This may settle after a few days.
  • Tell your doctor if troublesome.
  • If you have been diarrhoea and are also taking the oral contraceptive pill, let your doctor or pharmacist know.
  • Vaginal itching, soreness or discharge (thrush)
  • Ask your doctor or pharmacist for advice.
  • Signs of problems with your liver such as yellow skin and eyes, dark urine and stomach pain
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • Signs of allergic reaction such as skin rash, itching, swelling of the lips, face, and mouth or difficulty breathing
  • Tell your doctor immediately or ring HealthLine 0800 611 116
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product


Cefalexin interacts with a few important medications or herbal supplements, so check with your doctor or pharmacist before starting cefalexin. If you are taking the contraceptive pill, the effectiveness of the pill can be reduced if you are sick (vomiting) or have diarrhoea which lasts for more than 24 hours. If this happens, ask your doctor or pharmacist for advice about contraception over the next few days.

Learn more

For adults: cefalexin New Zealand Formulary Patient Information
For children: cefalexin New Zealand Formulary for Children


  1. Cefalexin New Zealand Formulary
  2. Antibiotics: choices for common infections BPAC, 2017

Additional resources for healthcare professionals

Cephalexin ABM Medsafe, NZ
Cefalexin Sandoz Medsafe, NZ
When is an allergy to an antibiotic really an allergy? BPAC, NZ, 2015
Appropriate use of cephalosporins BPAC, NZ, 2011

Credits: Sandra Ponen, pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 24 Mar 2019