Cephalexin: Uses, Side Effects, and How to Take It
Cephalexin is a cephalosporin antibiotic used to treat certain bacterial infections, including infections of the throat, ears, skin, and urinary tract. It does not treat viral illnesses such as colds or flu, and should be used only when prescribed by a healthcare professional.
Take cephalexin exactly as prescribed and finish the full course unless your clinician tells you to stop. Contact a doctor or pharmacist if you have a serious allergic reaction, severe or persistent diarrhea, or other concerning symptoms.
Key facts at a glance
- ATC
- J01DB01
- Generic
- Cephalexin
- Class
- antibiotic-beta-lactam
- Brands
- Keflex
- Availability
- rx
- Pregnancy
- B
- Lactation
- safe
- Half-life (h)
- 1
- Onset (min)
- 60
- Duration (h)
- 6
- Routes
- oral
- Forms
- capsule, tablet
- Regions
- CN, US, EU, JP
- Monitoring
- allergy, renal-function
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
10 groupspregnancy
first trimesterno standard adjustment
use only if benefits outweigh risks
regular prenatal monitoring
Use with caution and monitor for adverse effects.
pregnancy
second trimesterno standard adjustment
use only if benefits outweigh risks
regular prenatal monitoring
Use with caution and monitor for adverse effects.
pregnancy
third trimesterno standard adjustment
use only if benefits outweigh risks
regular prenatal monitoring
Use with caution and monitor for adverse effects.
lactation
breastfeedingno standard adjustment
use with caution monitor infant for diarrhea or candidiasis
observe infant for gastrointestinal disturbances
Use with caution and monitor for adverse effects.
geriatric
elderlyadjust dose based on renal function
monitor renal function and adjust dose accordingly
定期监测肾功能和不良反应
Use with caution and monitor for adverse effects.
pediatric_age
childrendose based on body weight
standard pediatric dosing 25-50mg/kg/day divided every 6 hours
monitor for allergic reactions and gastrointestinal effects
renal_impairment
moderate impairmentreduce dose by 50% when CrCl 10-50 mL/min
reduce dose and monitor renal function
monitor renal function and serum drug levels if prolonged therapy
Use with caution and monitor for adverse effects.
renal_impairment
severe impairmentreduce dose by 75% when CrCl less than 10 mL/min
reduce dose significantly and extend dosing interval
close monitoring of renal function and drug levels
Use with caution and monitor for adverse effects.
hepatic_impairment
mild impairmentno adjustment needed
no dosage adjustment required
standard monitoring
hepatic_impairment
moderate impairmentuse with caution
monitor liver function tests
monitor hepatic function
Use with caution and monitor for adverse effects.
Statistics and clinical data
FDA approval year
Year when Cephalexin was first approved by the FDA
Drug class
Antibiotic class classification based on ATC system
Common uses
Common therapeutic uses for Cephalexin
Mechanism of action
Primary pharmacological mechanism of action
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 22, 2026. · Read our editorial policy