Cephalexin — what it is and when you’d use it

Cephalexin is a commonly prescribed antibiotic from the cephalosporin family. Doctors use it for many routine infections: ear infections, throat infections, skin and soft tissue infections, and some urinary tract infections. It fights bacteria by stopping them from building cell walls, which helps your immune system clear the infection faster.

Wondering if it’s the right drug for you? If your symptoms are clearly bacterial (fever, pus, worsening pain, not just a runny nose), your doctor may choose cephalexin. Viral illnesses like the common cold won’t get better with it.

How to take Cephalexin

Follow the exact dose your prescriber gives. Typical adult doses are 250–500 mg every 6–12 hours, with some regimens using 500 mg twice daily depending on the infection. A common pediatric dose is 25–50 mg per kg per day split into doses every 6–12 hours — your child’s doctor will calculate that for you.

Take it with a full glass of water. You can take cephalexin with or without food; if it upsets your stomach, try taking it with a meal. Finish the whole course even if you feel better after a day or two — stopping early can let the infection return or breed resistance.

Common side effects & warnings

Most people tolerate cephalexin well. The usual side effects are mild: diarrhea, nausea, stomach discomfort, and sometimes a yeast infection. If you get hives, swelling of the face or throat, breathing trouble, or a sudden severe rash, stop the drug and seek emergency care — those are signs of a serious allergic reaction.

If you have a known penicillin allergy, tell your doctor. Some people allergic to penicillin also react to cephalosporins, though cross-reaction rates are lower than older estimates suggested. Also mention any kidney problems — your dose may need to be lowered. Probenecid can raise cephalexin levels, so your doctor will check for interactions with other meds.

Watch for severe diarrhea or blood in the stool after or during treatment. That could signal Clostridioides difficile, which needs prompt medical attention. If you take blood thinners like warfarin, let your provider know; antibiotics can sometimes change how those drugs work.

Storage is simple: keep the capsules or liquid at room temperature, away from heat and direct sunlight. If you have the liquid form, check the label for refrigeration instructions and discard leftovers after the recommended period.

Quick checklist: take the full course, tell your doctor about allergies and kidney problems, watch for allergic signs and severe diarrhea, and avoid keeping unused pills for later. If symptoms don’t improve in 48–72 hours or if they get worse, call your provider — you may need a different antibiotic or further tests.

Have specific questions about dose for a child, pregnancy, or chronic conditions? Ask your healthcare provider — they can tailor the advice to your situation.