Cefalexin
Cefalexin is a first-generation cephalosporin used for skin and soft tissue infections, some urinary infections, and other susceptible infections per guidelines. It is not the same as penicillin but has related allergy cautions in some people.
This medicine is part of the Antibiotics (selected) category.
Generic name: cefalexin
Quick answers
Short replies to searches people often run before speaking to a clinician. For the overview of what the medicine is used for, see the short summary under the page title above.
What is it for?
Cefalexin is a first-generation cephalosporin used for skin and soft tissue infections, some urinary infections, and other susceptible infections per guidelines.
How long does it take to work?
Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review.
What are common side effects?
Diarrhoea, nausea, thrush, or mild rash.
Can you take paracetamol or ibuprofen with it?
Ask your GP or pharmacist before taking Cefalexin with paracetamol or ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
More about what Cefalexin is used for
Cefalexin is a first-generation cephalosporin used for skin and soft tissue infections, some urinary infections, and other susceptible infections per guidelines.
It is not the same as penicillin but has related allergy cautions in some people.
How does Cefalexin work, and how long does it take to work?
It interferes with bacterial cell wall formation, killing susceptible bacteria.
Resistance patterns guide choice — cultures may change the prescription.
How and when should you take Cefalexin?
Capsules or liquid as directed, often with food to reduce stomach upset. Shake liquids well and measure accurately.
Complete the prescribed course.
What are the common side effects of Cefalexin?
Diarrhoea, nausea, thrush, or mild rash.
Serious side effects of Cefalexin — when to get urgent help
Seek urgent help for bloody diarrhoea, severe abdominal pain, or allergic reactions.
What if you miss a dose of Cefalexin?
Take when remembered; space remaining doses; do not double.
Who should not take Cefalexin?
Severe cephalosporin allergy. Caution if severe immediate penicillin allergy — discuss with prescriber.
Can you take paracetamol or ibuprofen with Cefalexin? — other interactions
Metformin can interact with iodinated contrast in some contexts; for cefalexin courses, usual diabetes monitoring continues.
Cefalexin in pregnancy and breastfeeding
Often used when needed — discuss with your prescriber.
Blood tests and monitoring on Cefalexin
Kidney dose adjustment if renal impairment.
What might your GP prescribe instead of Cefalexin?
Amoxicillin, Doxycycline, or Nitrofurantoin for UTIs may be alternatives depending on sensitivities.
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Reviewed by UK registered pharmacists for accuracy and clarity. Content is informational only.
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Frequently asked questions about Cefalexin
People also ask — common Google searches
- What is Cefalexin used for?
- Cefalexin is a first-generation cephalosporin used for skin and soft tissue infections, some urinary infections, and other susceptible infections per guidelines. It is not the same as penicillin but has related allergy cautions in some people.
- How long does Cefalexin take to work?
- Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review. Always follow your prescriber’s follow-up plan.
- Can you take Cefalexin with paracetamol or ibuprofen?
- Ask your GP or pharmacist before taking Cefalexin with Paracetamol or Ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
- What are the side effects of Cefalexin?
- Diarrhoea, nausea, thrush, or mild rash. See the sections below for more detail, including serious side effects and when to seek urgent help.
- Can I take cefalexin if I am penicillin allergic?
- Some people tolerate cephalosporins despite penicillin allergy; others react — always tell your prescriber the exact reaction you had.
- Does cefalexin affect the pill?
- The antibiotic itself is not a classic enzyme inducer, but vomiting or diarrhoea can reduce contraceptive reliability — follow missed-pill advice.
Need personalised advice?
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Often used with
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