What is the recommended duration of treatment with Keflex (cefalexin) for an adult patient with a urinary tract infection (UTI)?

Duration of Keflex (Cephalexin) for UTI

For uncomplicated cystitis in adults, treat with cephalexin for 7 days, which is the standard duration supported by FDA labeling and clinical guidelines. 1

Treatment Duration by UTI Type

Uncomplicated Cystitis (Simple Bladder Infection)

• 7 days is the recommended duration for uncomplicated cystitis in patients over 15 years of age 1
• The FDA label specifically states cystitis therapy should be continued for 7 to 14 days, with 7 days being appropriate for straightforward cases 1
• Guidelines recommend treating acute cystitis episodes with "as short a duration of antibiotics as reasonable, generally no longer than seven days" 2

Complicated UTI

• 7 days for patients with prompt symptom resolution 2
• 10-14 days for those with delayed response, regardless of whether a catheter remains in place 2
• The European Association of Urology recommends 7-14 days for complicated UTI, with 14 days particularly for men when prostatitis cannot be excluded 2
• Recent evidence supports that 5-7 day courses are as effective as 10-14 day courses for complicated UTI 2

Catheter-Associated UTI

• 7 days with prompt symptom resolution 2
• 10-14 days with delayed response 2
• For younger women (≤65 years) with catheter-associated UTI without upper tract symptoms after catheter removal, a 3-day regimen may be considered 2

Dosing Considerations

Standard Dosing

• 500 mg every 12 hours is the FDA-approved regimen for uncomplicated cystitis 1
• Recent evidence confirms twice-daily dosing (500 mg BID) is as effective as four-times-daily dosing (500 mg QID) for uncomplicated UTI, with no difference in treatment failure rates (12.7% vs 17%, P=0.343) 3
• The twice-daily regimen may improve adherence without compromising efficacy 3

Alternative Dosing

• For more severe infections, 250 mg every 6 hours (four times daily) may be used 1
• Daily doses should remain within 1-4 grams per day 1

Key Clinical Pitfalls

Common mistakes to avoid:

• Do not extend treatment beyond 7 days for uncomplicated cystitis unless there is documented delayed response—this increases resistance risk without improving outcomes 2
• Obtain urine culture before starting therapy to guide treatment, especially in complicated UTI where resistance is more likely 2
• Do not treat asymptomatic bacteriuria in non-pregnant patients—this provides no benefit and promotes resistance 2
• Replace indwelling catheters that have been in place ≥2 weeks before treating catheter-associated UTI, as biofilm on old catheters reduces treatment efficacy 2

When to Extend Treatment

Extend to 10-14 days if:

• Patient remains febrile beyond 72 hours 2
• Symptoms persist or worsen during initial treatment 2
• Male patient where prostatitis cannot be excluded 2
• Underlying urological abnormality cannot be corrected 2

Evidence Quality Note

The 7-day duration recommendation is based on FDA labeling (highest authority for drug use) 1 and supported by multiple international guidelines from the Infectious Diseases Society of America 2, American Urological Association 2, and European Association of Urology 2. Recent research confirms shorter courses (5-7 days) are non-inferior to longer courses (10-14 days) for most UTI types 2, supporting the trend toward shorter durations to minimize resistance development.