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How and when to take cefalexin - Brand name: Keflex

Always take cefalexin as a doctor or pharmacist has told you.

Dosage

Cefalexin comes as tablets, capsules and a liquid that you swallow.

Your dose of cefalexin will depend on why you're taking it but for most infections, adults usually take 500mg, 2 or 3 times a day.

Your dose may be higher if you have a severe infection and be lower for children.

How to take it

If you're taking cefalexin capsules or tablets, swallow them whole with a drink of water. Do not chew or break them.

If you or your child are taking cefalexin as a liquid, it will usually be made up for you by a pharmacist. The medicine will come with a plastic syringe or medicine spoon to help you measure the right dose. If you do not have one, ask a pharmacist for one. Do not use a kitchen teaspoon as it will not measure the right amount.

You can take cefalexin with or without food.

Try to space the doses evenly throughout the day. If you take it 3 times a day, this could be first thing in the morning, mid-afternoon and at bedtime.

How long to take it for

Your doctor will tell you how long to take cefalexin for, as this can vary depending on the type of infection you have.

Cefalexin is generally used for a short time to treat an infection. It can also be used long-term to prevent infections from coming back.

For some types of infection, you may need to take cefalexin for at least 10 days.

Tell your doctor if you do not start to feel better after taking cefalexin for 2 to 3 days, or if you feel worse at any time.

Do not stop taking it before you're supposed to, as there's a risk the infection could come back. It also gives any remaining bacteria a chance to change or adapt, which means the antibiotic could stop working. This is known as antibiotic resistance.

Important

Keep 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.

If you forget to take it

If you forget to take a dose, take it as soon as you remember, unless it's nearly time for your next dose. In this case, skip the missed dose and take your next dose at the usual time. Try to leave a gap of at least 4 hours between doses.

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 also ask a pharmacist for advice on other ways to remember your medicines.

If you take too much

Taking 1 extra dose of cefalexin is unlikely to harm you or your child.

Speak to a pharmacist or doctor if you're worried or you take 2 extra doses or more.

Page last reviewed: 5 April 2023
Next review due: 5 April 2026