Cefalexin is rapidly and almost completely absorbed from the gastrointestinal tract with oral administration. Absorption is slightly reduced when it is taken with food and the medication can be taken without regard for meals. Peak levels of cefalexin occur about 1 hour after administration. Maximal levels of cefalexin increase approximately linearly over a dose range of 250 to 1,000 mg.
Like most other cephalosporins, cefalexin is not metabolized or otherwise inactivated in the body.
The elimination half-life of cefalexin is approximately 30 to 60 minutes in people with normal renal function. Therapeutic levels of cefalexin with oral administration are maintained for 6 to 8 hours. For this reason, cefalexin is typically administered once every 6 to 12 hours depending on the indication. More than 90% of cefalexin is excreted unchanged in the urine within 8 hours.