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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.

Possible side effects of cephalexin

  • 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

These are the most common side effects, but there may be others. Please report all side effects to the doctor or nurse.

In case of a severe side effect or reaction, call the doctor, nurse or pharmacist at 595-3300. If you are outside the Memphis area, dial toll-free 1-866-2STJUDE (1-866-278-5833), and press 0 once the call is connected.

Special instructions for cephalexin

  • 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.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

ATTENTION: If you speak another language, assistance services, free of charge, are available to you. Call 1-866-278-5833 (TTY: 1-901-595-1040).

ATENCIÓN: si habla español, tiene a su disposición servicios gratuitos de asistencia lingüística. Llame al 1-866-278-5833 (TTY: 1-901-595-1040).

تنبيه: إذا كنت تتحدث باللغة العربية فيمكنك الاستعانة بخدمات المساعدة اللغوية المتوفرة لك مجانا. .يرجى الاتصال بالرقم. 5833-278-866-1  (الهاتف النصي: 1040-595-901-1).