Cefalexin

General Information

First-generation cephalosporin

Do NOT use if patient has a history of severe penicillin allergy. If in doubt, discuss with Micro/ID.

Formulary antimicrobial: For details see OUH netFormulary

For all information regarding interactions, contraception, pregnancy and breastfeeding and additional information, see BNF.

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Indication	Oral dose
Lower, uncomplicated UTI	500mg BD
Other indications (e.g. pyelonephritis, cellulitis)	1g TDS
Serious susceptible infections due to sensitive Gram-positive and Gram-negative bacteria	1.5g QDS

Dosing for cefalexin should be at the upper end of recommended ranges.

Renal impairment

eGFR (mL/min/1.73m²)	Where the usual dose is 500mg BD	Where the usual dose is 1g TDS	Where the usual dose is 1.5g QDS
41 and above	Dose as in normal renal function
10-40	250mg BD	1g BD	1g TDS
Less than 10	250mg OD	500mg OD	1g OD
HDF/High Flux/PD	Dialysed; give post-dialysis on dialysis days Dose as in eGFR less than 10ml/min/1.73m²

Note: Doses are based on Sanford Guide and Renal Drug Database

Hepatic impairment

No dose adjustment required.

Auribindo Pharma – Milpharm Ltd. Cefalexin 500mg capsules summary of product characteristics. Electronic medicines compendium. Last revision of the text 18/09/24. Accessed via www.medicines.org.uk Accessed 3/2/26.
British National Formulary. Cefalexin. BNF online accessed via www.medicinescomplete.com Accessed 3/2/26.
The Renal Drug Database. Cefalexin. Last updated 07/07/23. Accessed via https://renaldrugdatabase.com Accessed 3/2/26.
UKCPA Critical Care Group (2013) Drug dosing in extremes of body weight in critically ill patients. Accessed 3/2/26.
All-Wales Antimicrobial Pharmacists’ Group (2022) Antimicrobial dosing in extremes of body weight in adults. Accessed 3/2/26.
Sanford guide [online]. Cefalexin. Last updated 2/12/25. Accessed via https://webedition.sanfordguide.com Accessed 11/2/26

Last reviewed: 11 Feb 2026

Next review date: 09 Feb 2029

Author(s): AMST.