Cephalexin (Keflex) Administration with Food
Cephalexin can be taken with or without food, as it is acid-stable and food does not significantly affect its absorption or clinical efficacy. 1
Key Administration Points
Food has no clinically significant impact on cephalexin absorption - the FDA label explicitly states that cephalexin "is acid stable and may be given without regard to meals" 1
Absorption occurs rapidly regardless of food intake, with peak serum levels achieved approximately 1 hour after administration whether taken with or without food 1
Complete absorption occurs in the upper intestine (not the stomach), which explains why food timing is not critical for this medication 2
Practical Considerations
When to Consider Taking WITH Food
Patients experiencing gastrointestinal upset may benefit from taking cephalexin with food, as this can reduce nausea or stomach discomfort, though the medication itself causes minimal GI irritation 2
Patient convenience and adherence - allowing flexible dosing with or without food improves compliance, which is critical for antibiotic efficacy 1
Absorption Characteristics
70-100% of the dose is excreted unchanged in urine within 6-8 hours, demonstrating complete and reliable absorption regardless of prandial state 2
High urinary concentrations are achieved (500-1000 mcg/mL following 250-500 mg doses), far exceeding minimum inhibitory concentrations for common urinary pathogens 2, 3
Therapeutic tissue levels are rapidly achieved in most body compartments (except CSF and aqueous humor), independent of food intake 2
Clinical Bottom Line
Instruct patients to take cephalexin at whatever time is most convenient for them - with meals, between meals, or on an empty stomach - as absorption and efficacy remain consistent. 1 This flexibility distinguishes cephalexin from many other oral medications where food significantly impacts bioavailability, and represents a practical advantage for patient adherence.