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Cephalexin

Antibiotic

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What is cephalexin?

Cephalexin (also called Keflex®) is used to prevent or treat infections. It is available in 250-mg and 500-mg capsules and a mixed berry-flavored liquid suspension, all of which are taken by mouth.

How to take and store cephalexin

  • You may take cephalexin with or without food. If you have stomach pain, take cephalexin with food.
  • Shake the liquid well before you take it. Use an oral syringe or medicine cup to be sure you are taking the correct amount.
  • Store the liquid medicine in the refrigerator.
  • Discard the liquid medicine after 14 days or when the expiration date on the label tells you to do so.
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Possible side effects

  • Nausea, vomiting
  • Diarrhea
  • Rash
  • Loss of appetite
  • Headache
  • Stomach pain
  • Allergic reaction with the following symptoms: rash, hives, itching, chills, fever, swelling in facial area, and joint pain

Symptoms of an allergic reaction include: rash, hives, itching, chills, fever, headache, muscle ache, shortness of breath, coughing, tightness in the throat, swelling of the face or neck.

Not all patients who take cephalexin will experience these side effects. Common side effects are bolded, but there may be others. Please report all suspected side effects to your doctor or pharmacist.

Find more information on side effects.

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Tips for patients and families

Be sure to discuss all questions and instructions with your doctor or pharmacist. 

  • Before taking cephalexin, tell your doctor if you have had an allergic reaction to any other cephalosporin or penicillin antibiotics. If you have allergy symptoms (listed above) or you have severe or watery diarrhea, tell your doctor right away.
  • Finish all doses of this medicine as instructed by your doctor, even if you think your condition is better. Do not stop taking this medicine unless your doctor tells you to do so.
  • Do not take cephalexin while you are taking probenecid without telling your doctor. Probenecid may increase the levels of cephalexin in your body.
  • Cephalexin may cause a false-positive urine test result when checking your urine for sugar (glucose) levels.
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Always check the medication label. Many medicines look the same. Do not take any new medicine, including over-the counter medicines or supplements, without checking with your doctor or pharmacist. Talk to your doctor or pharmacist about what to do in the case of a missed dose, allergic reaction, or medical emergency. 

This information is not intended to be a complete guide and is not a substitute for talking with your provider. Medicine names, appearance, formulas, or availability may vary by clinic location. Always follow the instructions given by your care team.

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