Cephalexin: What It Is, How It Works, and What You Need to Know

When you’re dealing with a stubborn skin infection, a bad sinus cold, or a urinary tract issue, your doctor might reach for Cephalexin, a first-generation cephalosporin antibiotic used to treat bacterial infections. Also known as Keflex, it’s one of the most prescribed antibiotics worldwide because it works fast, is usually well-tolerated, and covers a broad range of common bacteria. Unlike some antibiotics that target only one type of germ, Cephalexin steps in when you’ve got a mix of staph, strep, or other gram-positive bugs causing trouble.

It’s not a cure-all, though. Cephalexin won’t touch viruses like the flu or a cold, and it’s not the first choice for certain resistant infections. But for things like cellulitis, boils, ear infections in kids, or bladder infections, it’s often the go-to. People take it for 7 to 14 days, usually two to four times a day. Missing a dose or stopping early can let bacteria come back stronger—that’s why sticking to the schedule matters more than you think. Side effects? Mild stomach upset, diarrhea, or nausea are common, but serious reactions like allergic rashes or trouble breathing are rare. If you’re allergic to penicillin, you might still be able to take Cephalexin, but your doctor will check carefully—cross-reactivity isn’t guaranteed, but it’s a risk worth discussing.

What’s interesting is how Cephalexin fits into the bigger picture of antibiotics. It’s older than newer drugs like amoxicillin-clavulanate or azithromycin, but it’s still widely used because it’s cheap, effective, and doesn’t mess with gut flora as much as some alternatives. In fact, many of the posts you’ll find here compare Cephalexin to other treatments—like when it’s better than doxycycline for skin infections, or why it’s preferred over clindamycin in certain cases. You’ll also see real-world advice on what to do if it doesn’t work, how to manage side effects, and even how it interacts with other meds like blood pressure pills or diabetes drugs. It’s not just about taking a pill—it’s about understanding when it’s the right tool, when it’s not, and how to use it safely.

Whether you’ve been prescribed Cephalexin or are just trying to understand why your doctor chose it over another option, the articles below give you the clear, no-fluff facts you need. You’ll find comparisons with other antibiotics, real patient experiences, warnings about misuse, and tips to avoid common mistakes. No jargon. No hype. Just what works—and what doesn’t.