Cephalexin
Capsule or syrup
Quick Summary
Cephalexin works well against bacteria that commonly infect skin and soft tissues.
Medical Uses
How it's taken
Take it at regular intervals, with or without food.
Take it for the full course, even if you feel better, unless your doctor tells you otherwise. Don't share antibiotics or keep leftovers.
Your doctor decides the right dose for you and how long to take it.
Your doctor decides the right dose for you. Follow their instructions and the label.
Common Side Effects
Diarrhoea
Common.
Nausea
Stomach upset.
Rash
Possible allergy.
Interactions
Metformin
Levels may rise slightly.
Critical Warnings
Allergy
Black Box Warning: Tell your doctor about penicillin or cephalosporin allergy.
Severe or bloody diarrhoea
Can be a sign of a serious bowel infection. Contact a doctor.
Severe allergic reaction
Black Box Warning: Swelling of the face or throat, difficulty breathing or a widespread rash: get emergency help.
Antibiotic resistance
Using antibiotics when they aren't needed makes them less effective for everyone.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Cephalexin: drug information(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Cefalexin: antibiotic used for infections such as pneumonia(opens in a new tab) · NHS