Cephalexin: What it treats and how to use it safely

Cephalexin is a common oral antibiotic (a first-generation cephalosporin) used for skin infections, ear infections, some respiratory infections, and simple urinary tract infections. If your doctor prescribes it, the goal is fast symptom relief and stopping the infection from spreading.

Here’s what you need to know so you use cephalexin correctly and avoid avoidable problems.

How to take cephalexin

Most adults take 250–500 mg every 6–12 hours depending on the infection. For kids, the dose is weight-based and written as mg per kg. Take the capsules or liquid with food if it upsets your stomach. Stick to the schedule — skipping doses makes treatment less effective and raises resistance risk.

Finish the full course even if you feel better after a day or two. Stopping early can let bacteria come back stronger.

Side effects, warnings, and interactions

Common side effects are mild: nausea, diarrhea, and stomach pain. If you get a rash, swelling of the face or throat, or trouble breathing, stop the drug and get medical help right away — that can be an allergic reaction. If diarrhea is severe or bloody, contact your doctor; antibiotics can trigger C. difficile, a serious gut infection.

People with penicillin allergies can sometimes react to cephalosporins, though most tolerate it. Tell your prescriber about any drug allergies. Cephalexin is cleared by the kidneys, so dose changes may be needed if you have reduced kidney function. Probenecid can raise cephalexin levels; always tell your provider about other medicines and supplements you take.

Pregnant or breastfeeding? Cephalexin is commonly used in pregnancy when needed, but check with your clinician before starting any antibiotic.

When you should call the doctor: fever that won’t come down, spreading redness around a wound, worsening symptoms after 48–72 hours on treatment, or any sign of an allergic reaction.

If you miss a dose, take it as soon as you remember unless it’s almost time for the next dose. Don’t double up to catch up.

Storage is simple: keep the liquid suspension refrigerated only if the label says so; capsules and tablets should be stored at room temperature away from heat and moisture.

Thinking about buying cephalexin online? Remember it’s a prescription drug in most countries. Use only licensed pharmacies that ask for a prescription, show clear contact info, and have verified reviews or accreditation. Avoid sites that sell antibiotics without any medical check or offer unusually low prices — counterfeit meds are a real risk.

Want help finding reliable information or safe pharmacies? Browse our guides on buying meds online and comparing pharmacies, or talk with a pharmacist before you order. If your symptoms are severe, get medical care in person rather than self-treating.