Cephalexin is typically taken every 6 hours (four times a day) or every 12 hours (twice a day), depending on the type and severity of infection. The standard adult course lasts 7 to 14 days. Your prescriber chooses the exact schedule based on what’s being treated, so the frequency can vary from person to person.
Standard Adult Dosing Schedules
For most infections in adults and teens 15 and older, the usual dose is 250 mg every 6 hours. That means four doses spread across the day, roughly at breakfast, lunch, dinner, and bedtime. An alternative schedule of 500 mg every 12 hours is also used, which cuts it down to just two doses a day. Both approaches deliver the same total amount of the drug over 24 hours (about 1,000 mg).
For more severe infections, the daily total can go higher, up to 4 grams per day, split into two to four equally spaced doses. Infections commonly treated with cephalexin include skin infections, urinary tract infections, ear infections, respiratory tract infections, and bone infections. Strep throat and other streptococcal infections generally require at least 10 days of treatment to fully clear the bacteria and reduce the risk of complications.
Why Spacing Matters
Cephalexin has a short half-life of roughly 30 to 70 minutes, meaning your body clears it from the bloodstream quickly. Evenly spaced doses keep the drug at effective levels throughout the day. If you’re on a four-times-daily schedule, aim for doses about 6 hours apart. If you’re taking it twice daily, space doses about 12 hours apart.
You don’t need to wake up in the middle of the night to hit exact intervals. A practical approach is to tie doses to your daily routine (meals and bedtime for a four-times-daily schedule, or morning and evening for twice daily) and keep them as consistent as possible.
Dosing for Children
Children’s doses are based on body weight rather than a fixed number of capsules. The standard range is 25 to 50 mg per kilogram of body weight per day, divided into equal doses given every 8 or 12 hours. For severe infections, including bone and joint infections, that daily total can increase to 50 to 100 mg per kilogram. Ear infections in children often call for the higher end of the range, around 75 to 100 mg per kilogram per day.
Cephalexin for children usually comes as a liquid suspension, which should be kept in the refrigerator and thrown away after 14 days, even if there’s medication left.
How Long a Typical Course Lasts
Most cephalexin prescriptions run 7 to 14 days. The exact length depends on the infection. Strep throat and other streptococcal infections require a minimum of 10 days to prevent the bacteria from bouncing back. Uncomplicated skin infections or urinary tract infections may need a shorter course, while bone infections can require longer treatment.
Finishing the full course matters even if you feel better within a few days. Stopping early can leave behind bacteria that are harder to treat if the infection returns.
What to Do If You Miss a Dose
If you realize you missed a dose, take it as soon as you remember. The one exception: if your next scheduled dose is coming up soon, skip the missed one and continue with your regular schedule. Never double up to compensate for a missed dose. Doubling increases the risk of side effects without meaningfully improving how the drug works.
Kidney Function and Dose Adjustments
Your kidneys are responsible for clearing cephalexin from your body. If your kidneys aren’t working at full capacity, the drug stays in your system longer, and your prescriber may reduce the dose or extend the time between doses to prevent buildup. This is something your provider will determine based on lab work, so you won’t need to adjust anything on your own.
Storage
Capsules and tablets can be stored at room temperature, away from heat and moisture. Avoid keeping them in the bathroom, where humidity tends to be high. The liquid suspension needs refrigeration and should be discarded 14 days after it’s mixed, regardless of how much is left in the bottle.