Missed Dose of Keflex (Cephalexin): What to Do
If you cannot remember whether you took your scheduled Keflex dose, take the dose immediately unless it is almost time for your next scheduled dose—in that case, skip the missed dose and resume your regular schedule. 1
Immediate Action Algorithm
Take the dose now if:
- More than 6 hours remain until your next scheduled dose (for standard twice-daily dosing) 1
- You realize the missed dose within 2-3 hours of when it should have been taken 1
Skip the dose and wait if:
- Less than 6 hours remain until your next scheduled dose 1
- You are uncertain about timing and your next dose is approaching 1
Never double up doses to make up for a missed dose, as this increases the risk of adverse effects without improving efficacy 1
Critical Principles for Antibiotic Adherence
The FDA label explicitly warns that skipping doses or not completing the full course of therapy may:
- Decrease the effectiveness of the immediate treatment 1
- Increase the likelihood that bacteria will develop resistance and will not be treatable by cephalexin or other antibacterial drugs in the future 1
Cephalexin should be taken exactly as directed to maintain therapeutic drug levels and ensure bacterial eradication 1
Practical Strategies to Prevent Future Missed Doses
Set up reminder systems:
- Use smartphone alarms timed to your dosing schedule 1
- Link doses to daily activities (e.g., meals, bedtime) for twice-daily regimens 2
- Use pill organizers with day/time compartments to track whether doses were taken 1
Standard dosing intervals for cephalexin are typically every 6-12 hours depending on the infection being treated, with twice-daily dosing (every 12 hours) being common for many infections 2, 3
When to Contact Your Healthcare Provider
Seek medical advice if:
- You have missed multiple doses and are concerned about treatment failure 1
- You develop new or worsening symptoms despite taking the antibiotic 1
- You experience adverse effects such as severe diarrhea, rash, or allergic reactions 1, 4
The medication should be taken for the full prescribed course even if you feel better early in treatment, as stopping prematurely increases resistance risk 1