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Common questions about cefalexin - Brand name: Keflex

How does cefalexin work?

Cefalexin belongs to a group of medicines called cephalosporin antibiotics. It works by killing the bacteria that causes the infection.

Cefalexin can treat a wide range of bacteria, so it works well for a variety of infections, such as chest, skin or urinary tract infections (UTIs).

When will I feel better?

For most infections, you'll start to feel better in a few days, but this depends on the type of infection you have.

It's important that you take the full course your doctor has advised, even if you feel better. It will stop the infection coming back.

What if I do not get better?

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

What is antibiotic resistance?

If you need to take antibiotics like cefalexin often, some of the bacteria may change and become less affected by the antibiotic. This is called antibiotic resistance. If your symptoms start to get worse or do not improve at all, tell your doctor or a pharmacist.

Do not stop taking your medicine early, even if you feel better, as this makes it more likely that the infection will come back and the bacteria will be resistant to cefalexin.

What will happen if I stop taking it?

Carry on taking cefalexin until you've completed the course, even if you feel better.

When you stop too soon, any bacteria left can start to multiply, which may cause another infection. There's also a risk that cefalexin stops working on these bacteria and you may need a different antibiotic next time.

How does it compare to other antibiotics?

Cefalexin belongs to a group of antibiotics called cephalosporins. This group also includes other antibiotics such as cefradine, cefuroxime and ceftazidime.

Different antibiotics are used to treat different infections. Your doctor will choose the antibiotic based on which bacteria they think is causing your infection.

Cefalexin can treat a wide range of bacteria, so it works well for a variety of infections, such as chest, skin or urinary tract infections (UTIs).

Cefalexin can only be given as capsules, tablets or a liquid, but some other antibiotics can be given as injections.

Will it affect my contraception?

Cefalexin does not stop any type of contraception from working, including the combined pill and emergency contraception.

However, if cefalexin makes you have severe diarrhoea for more than 24 hours, your contraceptive pills may not protect you from pregnancy. Look on the pill packet to find out what to do.

Find out more:

Can I drive or ride a bike?

Yes, cefalexin will not affect you being able to drive or ride a bike.

Can I drink alcohol while taking cefalexin?

Yes, you can still drink alcohol with cefalexin.

Are there any foods and drink I should avoid?

No, you can eat and drink normally while taking cefalexin.

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