Cefalexin
Also known as: Keflex, Ceporex
What it's for
Cefalexin is an antibiotic for skin infections, urinary tract infections, and respiratory infections. It belongs to the cephalosporin family of antibiotics.
Comes as: Capsules, tablets, or liquid
How to take it
- Adults: Usually 250mg to 500mg, 2 to 4 times a day.
- Take with or without food.
- Space doses evenly through the day.
- Complete the full course.
Doses here are typical. Always follow the instructions from your prescriber or on the packet — they come first.
Common side effects
- Diarrhoea
- Feeling sick or stomach pain
- Headache
- Dizziness
The leaflet inside the packet lists all known side effects.
Important safety points
- Tell your doctor if you are allergic to penicillin (some cross-reaction possible)
- Tell your doctor if you have kidney problems
- Can reduce effectiveness of the contraceptive pill
Get medical help urgently if…
- You have severe diarrhoea or blood in your stool
- You have a severe skin rash or blistering
- You have swelling of your face, lips, or tongue
- You have difficulty breathing
Call NHS 111 for urgent advice, or 999 if someone is seriously unwell.
Before you act on anything here
This page is general information, written to help you understand — it is not personal medical advice and it cannot tell you what is right for you. Talk to your own GP, pharmacist or nurse about your own health.
- Need help now but it's not an emergency? Call NHS 111 or use 111.nhs.uk.
- Emergency? Call 999 or go to A&E.