Cephalexin Dosage: What You Need to Know About Strengths, Timing, and Safety

When your doctor prescribes Cephalexin, a first-generation cephalosporin antibiotic used to treat bacterial infections like skin infections, urinary tract infections, and respiratory tract infections. Also known as Keflex, it's one of the most commonly prescribed antibiotics for mild to moderate infections because it's effective, affordable, and well-tolerated by most people. But getting the dosage right matters—too little won’t clear the infection, and too much raises your risk of side effects like nausea, diarrhea, or even yeast infections.

Cephalexin comes in capsules, tablets, and liquid form, with strengths ranging from 250 mg to 500 mg. For adults, the typical dose is 250 mg every 6 hours, or 500 mg every 12 hours, depending on the infection. For more serious infections like bone or joint infections, your doctor might bump it up to 1,000 mg every 6 hours. Kids get doses based on weight—usually 25 to 50 mg per kilogram per day, split into 3 or 4 doses. Always follow your prescription exactly. Don’t stop taking it just because you feel better; incomplete courses are a major reason bacteria become resistant.

It’s also important to know when to take it. Cephalexin works best on an empty stomach—about an hour before or two hours after meals—because food can slow absorption. But if it upsets your stomach, taking it with a light snack is fine. Avoid alcohol while on Cephalexin; it doesn’t cause a dangerous reaction like some antibiotics, but it can make side effects like dizziness or stomach upset worse. And if you’re on birth control, know that antibiotics like Cephalexin might reduce its effectiveness, so use backup protection during treatment and for a week after.

Some people worry about allergies. If you’ve had a severe reaction to penicillin, you might also react to Cephalexin—about 10% of penicillin-allergic patients do. Watch for rashes, swelling, or trouble breathing. If you see any of these, stop the medicine and call your doctor right away. For most people, though, Cephalexin is safe and straightforward. It’s not for viral infections like colds or flu. Using it when it’s not needed doesn’t help you and hurts everyone by making antibiotics less effective over time.

What you’ll find below are real, practical guides that answer the questions most people have: How long should you take it? Can you drink coffee or take vitamins with it? What if you miss a dose? Is it safe during pregnancy? How does it compare to amoxicillin or azithromycin? These posts don’t repeat the same info—they give you different angles, real-life experiences, and clear comparisons so you know exactly what to expect and how to stay safe.