Question: how long do side effects from keflex last?
Answer: Half-Life of Keflex (Cephalexin) Keflex has a half-life of eight hours before being excreted in the urine. The typical dose of Keflex is 250 mg every six hours, with treatment lasting from 7 to 14 days. In healthy patients with more widespread infection, doses may be increased to 500 mg every 12 hours.